Oct. 8, v1946. F_ A, MQRRl‘s 2,409,145 CONTROL AND TRIGGER CIRCUIT FOR TELEPHONE SYSTEMS AND >'.l‘I-IEÈ LIKE Filed sept. 2e, i944 /16 04 16 4 sneetsfsneet 1 /152 136? 7/LOIT'ANHE0/SR N5TSGPHEOM/'IP . IN VEN TOR. - F19H/VK H. MOR/‘PAS’ BY Hf7'OHNE Y Í. â, ì946. F, A_ MORRlS 2,409,145 CONTROL AND. TRIGGER CIRCUIT FOR TELEPHONE SYSTEMS AND THE, LIKE Filed Sept. 26,> 1944 4 sheets-sheet 2 INVEN TOR. FFH/VK H MORE/5 Oct. 8, 1946. F. A_MoRRls 2,409,145 CONTROL AND TRIGGER CIRCUIT FOR TELEPHONE SYSTEMS AND THE LIKYE1 Filed Sept. 26, 1944 MSN ASN .nu QQ N. NN NM, 4 Sheets-Sheet 3 . 8, 1946. 2,409,145 F. A. MORRIS CONTROL AND TRIGGER CIRCUIT FOR TELEPHONE'SYSTEM‘S AND THE LIKE Filed Sept. 26, 1944 „ i T- car-off /Paßy 6 _ l 4 Sheets-Sheet 4 60 60 jr' 4 f » Y .sro/’P//ve /mfïy ' „20 R . . Ã‘ UNE c//i’cz//ï I 54 (_, (9 I L//vE F//voE/i’ 39 60 j /sr L//vk *Lv f 2ND L//vx ML 33 60j _/ 6 (_) / 7 5 46 K 1,83 . __¿__ 12,27 H') L1- (+) 163 y. 6 [44 I / 1501/. 133 a ~ 147 1330 _ Í_4_.__L4 166 147 5 _i’î/ìñî 124 133 ? JUPERIMPOSED SUPFR/Mßosfo 132 , Gf/VERHTOR /Nrfmvaprfo /Nrá-RRUP T50 x 1,23 î*_i.„_____ L GFA/ERHT‘o/ï l . M5575@ . @Roz/No _L-/Wyx ï 9 1,24 Y 12m 200` , e) ï .f 419 V. y l J30~-- '\/\(V\, le@ 202 20] IN VEN TOR. l ffm/vx H. Mom/5 __Q BY l/ Á‘ v / Í f ‘Y Leef-ä Patented Get. 8, 1946 UNTE 2,409,145 STATES FATENT OFFICE 2,409,145 CONTROL AND TRIGGER CIRCUIT FOR TELEPHONE SYSTEMS AND THE LIKE Frank A. Morris, Rochester, N. Y., assignor to Stromberg-Carlson Companyyltochester, N. Y., a corporation of New York ' Application September 26, 1944, Serial No. 555,850 20 Claims. (C1. 179-4752) 1 2 rlîhis invention relates to stopping, triggering and testing circuits which are particularly useful in telephone systems and the like. In such systems and especially in automatic telephone systems, it is important that the auto generalized application than the speciñc arrange ment shown in Fig. 3. The novel control circuits herein shown, are applicable to many fields of use, but for con venience in disclosure they are shown incorpo rated in an automatic telephone system. This system is herein illustrated as being of a size em matic switch means employed therein be prompt ly stopped as soon as a given switching connection ploying only ñnder and connector switches. has been effected. Also in such systems, it is nec However, the number of lines served by the sys essary to test certain equipment, such as lines, trunks or allotters to determine whether or not 10 tem can be increased by the addition of selector such equipment should be seized for use. Such switches in the >manner well known. ' The finder and connector switches herein ln testing should be effected in a reliable manner dicated, are of the construction disclosed in the and in an inñnitesimal period of time. Further patent to Lienaen No. 2,148,824, granted Febru more, both in automatic telephone systems and in manual systems as well, trigger circuits are es 15 ary 28, 1939, although other types of switches sential especially for tripping the ringing current having primary and secondary selecting move when the called subscriber answers. The main feature of the invention relates to ments may be used instead. The allotter herein indicated may be of the so-called ball-selector type, disclosed in the patent to Blomberg No. control circuits generally, wherein electric dis charge devices contribute to the reliability and 20 2,127,322, although other types of allotter switches may alternatively be used. markedly prompt action thereof. With this brief reference to the switch con Another feature of the invention relates to struction, it is believed that the invention will novel control circuits incorporating therein elec best be understood by describing the method of tric discharge devices, which circuits determine establishing a telephone connection from a tele the availability for use of telephone equipment, phone subscriber’s line, indicated at A, to a called govern the action of telephone switching appa subscriber’s line, indicated at B. When the sub ratus, and trigger the operations of telephone apparatus. The various features and advantages of the in vention will appear from the detailed description and claims when taken with the drawings in which Figs. 2 and 3. when arranged in the or der named, illustrate the novel circuits of this in vention incorporated in an automatic telephone system. Fig. l shows two typical telephone lines and duplicate allotter control means. Fig. 2 il lustrates an allotter and a portion of aline ñnder, certain of the brushes oi which are shown at the lower right of this ligure. At the left hand side of Fig. 3 there` are shown the remainder of the finder brushes, while at the center and at the right hand portion of this figure, there is shown the connector switch circuit. Fig. 4 is a schematic circuit arrangement illustrating in somewhat simpler form a low voltage “ñring” circuit for a gas-filled arc discharge device utilized to stop the finder switch in the system of Figs. l, 2 and 3. Fig. 5 is a simpliñed disclosure of the testing ar scriber at substation A removes his receiver from its switch-hook, a circuit is completed for ener 30 gizing the group line relay 5 which is common to a group of ten lines in the same tens group. This> circuit extends from ground, winding of the relay 5, upper back contact and armature of the cut-off relay 6, upper side of the calling line, thence, 35 through the calling substation and over the low er side of the calling line, lower` armature and back contact of the cutoiî relay 5, resisto-rs l and 8 in series to the negative side of battery. Con denser S is connected in parallel with the resistor .40 8 so that the drop across resistor 8 charges the condenser 9, thereby putting an identifying con dition on the calling line hunt terminal I0, in the terminal of the group of finder switches serving this line. The operation of the common line re 45 lay .'ê serves to start an allotted ñnder to search for the calling line, and also serves to place an identifying ground on the group level ll (Fig. 1) in the line under banks. It will be noted that the upper armature of the line relay 5 is provided rangement employed in the mentioned system, two links being shown to indicate the condition 50 with two contact springs I2 and I3 which close in sequence. This insures that the identifying prevailing when a busy line is tested. Fig. 6 is ground will be applied to the group level Contact a modified form of ringing trip arrangement or li in the line finder bank, before the line finder starts to move. The start of the line ñnder is used in the connector circuit of Fig. 3. Fig. ’7 illustrates a trigger circuit of somewhat more 55 elîected from ground at the upper armature of trigger circuit which can be substituted for that ' 2,409,145 3 group relay 5 and front contact I2 thereof, now closed, as well as the front contact I3 subse quently closed, thence, over conductor I4, arma ture and back contact of the relay I5, conductor I6, back contact and armature of relay> I'l, con ductor I8, winding of the allotter start relay I9, to negative battery. The operation of the al lotter start relay I9 applies ground at its upper armature and front contact for completing a cir 4 mature and back contact, opens the energizing circuit of the relay 23. This relay, it will be re called, is also sluggish in releasing its armatures. The purpose of this sluggishness is to provide a delay sufficient for the ñnder switch to come to rest definitely, after its primary hunting move ment and before its secondary hunting movement is started. However, after a very brief time, the slow-releasing relay Z3 does release and thereby cuit through the armature and back Contact of 10 completes a self-interrupting circuit for the sec the relay 2i), armature and back contact of the relay 2|, conductor 22, winding of the relay 23 to the negative side of battery. It should be pointed out that the relay 23 is sluggish not only in at ondary magnet ‘i5 extending from the negative ' side of battery, winding of this magnet, its arma ture and back contact, allotter brush l'sï, back contact and armature of relay 23, front contact tracting its armatures but also in releasing them. 15 and armature of relay 2|, now energized, back contact and armature cf relay 20, front contact The purpose of having the relay 23 sluggish in and armature of allotter start relay i3 to ground. operating, is to hold open its armature 24 and Under the control of this circuit, the secondary front contact for a slight interval, to insure that stepping magnet fit advances the nnder brushes the circuit of the primary stepping magnet of the 3l, £5, 39 and in their units or secondary 20 ñnder is not completed until the pre-impulse cir hunting direction. This hunting operation con cuit has an opportunity to function. The pre tinues until the brush ¿lil encounters the hunt impulse circuit is energized by ground, applied at terminal Iû (Fig. l) of the calling line. It Will the inner front contact and armature of the re» be recalled that when the subscriber of this line lay I9, conductor 25, allotter switch contact 23, conductor 2l, current limiting resistor 23, sec 25 initiated a call, he set up a condition whereby the condenser 9 was charged. Consequently, tion 29 of the link conductor, lower winding of when the ñnder brush riß encounters the hunt the combined battery feed and impulse relay 353, to terminal Iii, a circuit is completed from the nega the negative side of battery. Relay 3i) is energized tive side of battery, primary winding 48 of a in this circuit and at its upper armature and step-up transformer (Fig. 2), front contact and 30 front contact removes ground from release con armature 4S of the allotter start relay, conductor ductor 83 while completing an obvious circuit for El), allotter contact 5I, ñnder brush t0, hunt ter energizing the slow-releasing relay 3| of the minal I0, through the condenser S, to negative connector. Relay 3| thus operates and at its side of battery. This circuit discharges condenser armature 32 and front contact applies master ground for the various circuits or the connector. 35 9 through the primary winding 48 of the trans former. This discharge induces a voltage in the It will be recalled that the relay 23 is slow to op secondary winding 52 of the transformer which erate and that during the time that it is attract voltage is applied ,through the condenser 53 t'o ing its armature 2li, the pre-impulse circuit, as the starter anode 54 of the finder stopping arc described, has an opportunity to be completed. When, however, the armature 2li and front con tact of relay 23 is closed, a self-interrupting cir cuit is completed for the primary magnet ‘ät of the finder switch. This circuit extends from the 40 >discharge device 58. The arc discharge device is gas-ñlled and preferably of the cold cathode type, sold under the code 1G21. This device comprises the cold cathode 55, the starter anode 54 and the anode proper 55. The mentioned induced volt negative side of battery, winding of primary step ping magnet 34, its armature and back contact, 45 age, when applied to the starter anode 54, causes the ñnder stopping device 58 to conduct. As a through the normally closed olif-normal contacts result of this, the allotter control relay is ener 35, contacts 36 of the allotter switch, front con gized from the positive side of battery through tact and armature 2Q of relay 23, back contact the capacitive network 59 and 6G, winding of and armature ofrelay 2 I, back contact and arma ture of allotter relay 2i), front contact and arma 50 the relay 25, across the space between the anode 55 and cathode 55 of the discharge device 58, ture of relay I9, to ground. Under the control of conductor 7|, lower front contact and armature this circuit, the primary stepping magnet ad of relay |9 to ground. The relay 2€) is thus ener vances the tip brush 3l, ring brush 38, sleeve gized and at its inner upper armature and back brush 39 (at left of Fig. 3) and hunt brush liu contact, it interrupts the stepping circuit for the (at right of Fig. 2) in their primary or group se secondary stepping magnet 45 so that the brushes lecting movement. Also, the stepping magnet of the ñnder come to rest. The arrangement, advances the group selecting brushes 4| (at the just described, for stopping the secondary move right of Fig. 2) and ¿52 (at the left of Fig. 3) in ment of the iinder switch is shown in simplified their primary direction. The primary stepping magnet 34 continues to self-interrupt its operat 60 form in Fig. 4. It now becomes necessary to test the calling ing circuit and thereby advances the mentioned line to make sure that it has not been seized as ñnder brushes until the rlnder brush 4I encoun a called line by a connector, which condition may ters the level contact |I (upper left Fig. 1) of have arisen during the time that the finder switch the group of lines in which the calling line is lo cated. As soon as the brush lll encounters the 65 in question was hunting for the calling line. As soon as the allotter control relay 2€) operates, it contact |I, this completes a circuit from ground also completes the necessary circuit for testing at the armature and contact i2 of relay 5, group the busy or idle condition of the calling line, for contact II, finder brush 4I, allotter brush 43, the purpose just mentioned. The busy test is conductor 44, winding of allotter transfer relay 2 I, to the negative side ci battery. This energizes 70 accomplished by the cold cathode arc discharge device 5I, preferably similar in construction to the relay 2| and at its uppermost armature and the device 58, in cooperation with the busy test front contact it opens the self-interrupting cir circuit. When the starter anode causes the cuit of the stepping magnet 34, thereby stopping gas in the device to ionize the busy test circuit the primary movements of the nnder switch. Also, the operation of the relay 2| at its inner ar 75 extendsl from the source of high positive voltage 2,409, 145 5 6 of the order of 150 volts, anode B2, cathode 6A, lay 2li, conductor 56, allotter brush El, conductor 58, upper winding of the connector cut-through relay $3, ñnder sleeve brush 39, finder sleeve con tact Se', which is individual to the calling line, winding ci the cut-off relay 6 to the negative side If the finder busy test device 5l indicatesa busy condition on the calling line, brought about by a connector seizing this line during the hunting interval, this device will not become conductive and the connector cut-through relay 69 (Fig. 3) in series with it, will not be energized. The talk ing connection will thus not be cut through and of battery. when the allotter advance relay il’ operates, as conductor 55, armature and front contact of re Current ñows in this circuit and cnergizes the cut-off relay 6 to disconnect the will be described, and the allotter delay relay 23 group line relay l? from the control of the calling 10 releases, the pre-impulsing ground will be re line and also energizes the cut-through relay B9. moved, the connector battery feed and impulsing lît should be mentioned that the electron discharge relay gli and the connector delay relay 3l Will also device 6| is adjusted by means of a potentiometer release and the release signal will be returned to the line finder -release magnet 8l (at right of conductive when sufficient voltage appears be 15 2). This will release the link seized by the tween its cathode Gd and starter anode E53. When calling party and he will be able to talk through the busy test lead, including the conductors S6 and the connection established by the connector which S8 and iinder sleeve brush 39. is extended through had seized his line during the hunting interval. the sleeve terminal of the calling line in the mul Before describing the operation of the con tiple bank, the circuit is completed in such a way 20 nector in seizing the called line in response to that the sum of 15G volts plus 48 volts appears the dial impulses, it will be set forth how the P across its ~cathode and anode so that it will be across the device Si, if the line is in an idle condi tion. The potentiometer P is adjusted so that the allotter is released from this call in the course of the completion of the line ñnding operation and how the allotter preselects an idle link for a succeeding call. This is brought about when the allotter control relay 2D (Fig. 2) is operated, thereby completing a circuit from ground, upper iront contact and armature of relay I9, inner armature and front contact of relay 20, conductor this circuit, a voltage drop appears across the 22, winding of the slow operating relay 23 to the cut-off relay E s0 that the voltage on the sleeve negative side of battery. This relay is slow to terminal of the calling line in the multiple bank operate for the purpose of giving a suflicient in no longer appears to be 4S volts negative, as terval of time for the iinder busy test circuit schematically indicated in Fig. _5. Thus, any including the device 6| to operate. As soon as other busy test lead of another link circuit will f the relay 23 does operate, it closes a circuit from not encounter sufficient voltage on its busy test ground on the lowermost front contact and arma brush, to ionize the gas in its busy testing device ture of relay 2B, lower front contact and arma similar to El. rEhe time required for the busy ture of relay 23, upper winding of the relay l1, test to be completed and the line to be made per to the negative side of battery. LThe relay l1 is manently buey to any other link, is thus reduced 40 thus energized and at its upper, inner armature to the ionization time of the discharge device, a and back contact it opens the allotter start cir matter of microseconds, as compared with oper cuit which it will be recalled included the wind ing of the allotter start relay I9, thereby caus ating time or” a relay which may be several milli seconds. This shortening of the unguarded inter ing this relay to deenergize. Relay Il, at its val reduces the possibility of double connections. 45 lower armature and iront contact, closes a lock The cut~thrcugh relay ES its upper airma ing circuit for itself through its upper winding tures and front contacts, extends the calling line and through its lower armature and front con through the länder brushes 3l and 3B, through tact, to ground applied to conductor 18, through both windings in series of the impulse relay 3s, the armature and back contact of the allotter to ground and grounded battery respectively. 50 busy relay ‘19. It should be mentioned that discharge device (il will become conductive when these voltage conditions are present. When the device becomes conductive, the circuit is then completed and the cut-off relay o and cut-through relay @il become energized in series in the manner above described. When current begins to ñow in Also, the operation of the cut-through relay 69 this allotter busy relay 19 is normally operated at its armature 'lil and front contact, closes a locking circuit for itself from the master ground, through its lower winding, resistor "il to the nega is taken for use, relay ‘I9 deenergizes. The ener tive side of battery. Also, the cut-through relay at armature "i90: and front contact applies master ground _through the Finder sleeve brush 39 and to the terminal Sil' of the calling line (Fig. 1) thereby rendering the calling line busy and also locking up the cut-oil relay â. Master ground is also supplied through the armature lâ) and front contact of the cut-through relay 63, con ductor l2, normally closed fed-normal contact i3 o_f the connector, lower winding of the primary motion delay relay l?l of the connector, to the negative side of battery. Relay lll is of the slow releasing type. .es soon as relay 'li is operated, it applies a dial tone over conductor l5, armature and back contact of relay lili?, front Contact and armature of relay ld, conductor l5, condenser 'l‘l and thence over the ring side of the link and the as long as the link is idle but as soon as the link gizing circuit for the allotter busy relay 'I9 which 55 is closed as long as the link associated with this relay is idle, extends from the negative side of battery, upper winding of the relay i9, the allotter brush Se (at right of Fig. 2), armature and back contact of the ñnder release magnet 8l, armature 60 and back contact 82 of the connector release magnet, to be described, conductor 83, back con tacts and armatures of relays 3l and 3i) (Fig. 3) to ground. It will be noted that when the link is taken for use, this energizing circuit for the 65 allotter busy relay 'I9 is interrupted at the arma tures and back contacts of both relays 3G and 5 i . Vfhen allotter busy relay 19 releases, it places a ground on the conductor lß, this ground being applied over conductor Sli, back contact andA 70 armature of the allotter start transfer relay l5, to ground. As soon as'the relay l1 was ener calling line to the calling subscriber’s substation. gized, it interrupted the operating circuit of the This tone, of course, signals the calling subscriber allotter start relay I9. This relay deenergizes that the dial-controlled apparatus is in condition and at its uppermost armature and front con 75 tact interrupts the circuit which has been hold to receive dialling impulses. 2,409,145 7 ing the slow operating relay 23 (Fig. 2) in its operated condition. When the relay 23 releases, it completes a circuit for advancing the allotter to seize an idle link. This operating circuit effects the energization of the relay 85 from the nega tive side of battery, winding of this relay, back contact and armature of the allotter motor mag net 85, conductor 81, back contact and armature of relay 23, armature 88 and front contact of relay 8 mal, it opens its oñ normal contact 13 (top center Fig. 3). This interrupts the initial operating cir cuit of the relay 14, insuring that this relay will not reoperate until the connector switch has been fully restored to normal. However the relay 14 is maintained operated through its upper Wind ing during the reception of the remainder of the tens impulses. At the conclusion of the tens se ries of impulses, the relay 14 will deenergize be~ | 1, to ground potential that is now present on 10 cause its locking circuit is interrupted at the back contact and armature of the impulse relay 30. the conductor 18, as described above. Relay 85 is thus energized and at its front contact and arma As soon as the connector switch moved off nor mal in its primary direction, it closed a circuit ture, closes in multiple with its energizing cir through its normally open primary oiî normal cuit, an operating circuit for the motor magnet 86. This circuit extends from the negative side 15 contacts 91 and through its normally closed sec ondary oi'f normal contacts 98, high resistance, of battery, winding of this magnet, front contact lower winding of the slow releasing secondary and armature of relay 85 and thence over the delay relay 99, to the negative side of battery. conductor 81 and the remainder of the circuit, This relay is thus energized preparatory to re previously described, to ground potential present on the conductor 18. This operates the magnet 20 ceiving the units series of impulses. Thus, when the impulse relay 30 responds to the units series 85 to advance the allotter. Also, the armature of impulses, the secondary motor magnet |00 of the motor magnet 86 interrupts the circuit will be operated in a circuit extending from the of the relay 85. Thus, the relay 85 and 86 operate negative side of battery, conductor | 0|, low re together in a pulse assuring arrangement, some times referred to as flip-nop operation. Under 25 sistance winding of relay 99, its front contact and armature, back contact and armature of relay the control of this arrangement, the allotter 14, now released, front contact and armature of advances until the brush 80 of the allotter en counters the terminal associated with an idle relay 3| , back contact and armature of the im pulse relay 30 to ground. Thus, in response to link, which terminal will be characterized by the presence of ground potential thereon. This 30 each unit impulse, the mentioned circuit will be completed to operate the secondary motor mag ground potential is applied over the conductor similar to conductor 83 and thence over back con tacts and armtures of relays corresponding to 3| and 30 to ground. When an idle link is lo net which advances the brushes of the connector switch in their secondary direction. As soon as the secondary _delay magnet 99 operated, it closed cated, the mentioned ground potential is applied 35 a circuit from ground through its armature |0| through the allotter brush 80, lowermost arma ture and front contact of relay |1, low resistance and front contact, lower winding of the slow re leasing connector busy delay relay |02 to the negative side of battery. The operation of the Winding of the allotter busy relay 19 and the relay |02 disconnects the dial tone and closes negative side of battery. Also, ground is applied through the upper high resistance winding of this 40 a break point in the test circuit. Consequently, when the secondary delay magnet 99 releases at relay to the negative side of battery. The com pletion of the circuit through the lower winding of the conclusion of the series of units impulses, thereby closing a second break point in the tes this relay, which is of low resistance, insures that the relay will receive a surge of current, circuit, and when the connector brush 93 is rest causing it to operate promptly. The operation of 45 ing on the test terminal of the called line, the the relay-19, at its upper armature and back con testing of that line can be effected. If the called tact removes ground potential from the conductor line is idle, the starter anode |05 of arc dis 18 and thus insures that the relay 85 and the charge device |03 will become conducting in the allotter motor magnet 85 cease to operate. same manner as the arc discharge device 6|, as 50 It will be recalled that at the point where the described above. When discharge device |83 be dial tone had been applied to the calling line to comes conducting, a circuit from the positive indicate that the connector was in readiness to source of battery, anode |04, cathode |06 of the receive dial impulses, the description was inter device, lower winding of the busy test relay |01, rupted to explain how the allotter operated to lower armature and front contact of relay |02, assign an idle link for use. It will be understood, 55 armature |08 and back contact of relay 99, con however, that in normal operation these opera ductor |09, connector brush 93, sleeve terminal tions take place simultaneously. On receiving the ||0 (Fig. 1), winding of cut-off .relay ||| of the dial tone, the calling subscriber operates his d'al called line to the negative source of battery. sender to transmit impulses corresponding to the The relay |01 is operated in this circuit and at tens digit of the wanted number. In response to its upper front contact and armature locks itself each of these tens digit, the impulse relay 30 operated to master ground. The relay |31 at its releases its armature to complete a circuit for uppermost armature and front contact applies operating the primary stepping magnet 89 of the ground over conductor H2, back contact and ar connector. This circuit extends from the nega tive side of battery, winding of this magnet, con 65 mature |08, conductor |09, connector brush S3, sleeve terminal ||0, thereby locking up the cut ductor 90, through the very 10W resistance wind off relay |||. This application of ground to the ing (3 ohms) of the relay 14, its upper front sleeve terminal ||0 of the called line makes this contact and armature, front contact and arma line permanently busy to any other link. Relay ture of relay 3|, back Contact and armature of the impulse relay v3|) to ground. In response to 70 |01, when it operates, prevents the application of busy tone at its armature ||3 and back con each of the tens impulses, the stepping magnet tact. At the armatures ||4 and ||5 and iront advances the tip, ring and sleeve brushes 9|, 92 contacts of relay |01, the link is extended through and 93 and connector hunt brush 94 and also the tip and ring brushes 9| and 92 of the con the group brush 95 of the connector. As soon as the connector switch takes its ñrst step oiî nor 75 nector to the terminals of the called line, in readi d :2,409,145 iiess for applying the ringing current to this line. and front contacts, it v'closes break points in a circuit extending the battery through the Wind ings of the battery feed relay |33 to the called If the connector arc discharge device |03 indi cates a busy condition of the called line, this dis charge device will not become conductive and the connector busy test relay lill in series there with will not become energized. When the con nector b d ` y relay |92 then releases, busy tone will be extended through the armature i i3 and back contact or the connector busy test re lay lill, armature and back contact of the con~ 10 nector busy delay relay H82, conductor §26, ar mature and back contact of the connector pri mary motion delay relay M, conductor lâ, and through condenser l? to the ring side of the link and or" the calling line. 15 Ringing current is now applied 'to the called subscriber’s line from the ringing generator, through the ringing delay device H8, which ai' fords suiñcient time for the ringing trip heater type gas tetrode iig to become available for 0D 20 eration. The ringing circuit extends from the device llt, over conductor |29, upper armature and back contact or" the ringing trip relay lì’i, conductor i222, armature i iii and iront contact, through the tip brush 9| of the connector and 25 thence over the calling subscriber’s line and sta tion B, thence through the ring brush Q2 of the connector, front contact and armature H5, con duc-tor its, armature and back contact of trip relay |25, resistor läd to ground. Interrupted 30 superimposed ringing current is applied over the circuit just described to signal the called sub scriber at'B. During the time that the ringing current is being applied, a ringing tone is trans mitted back to the calling subscriber, this tone 35 being applied over conductors |22 and £25, ar mature and front contact or" relay itl, back con tact and armature of relay |522, conductor |26, back contact and armature or" relay lil, conductor le, condenser ll' and to the ring side of the call 40 ing end of the link to the calling subscriber’s substation. When the called party answers by removing subscriber’s line. VAt the armatures back contacts of relay i12 l, break points are introduced into the ringing circuit. The connection has thereby been established between the calling and the called subscriber’s line in readiness for tele phone conversation. . t the conclusion of the conversation when the calling subscriber replaces his receiver on its switch»hook, the impulse relay Se deenergizes. At its armature and iront Contact, it interrupts the circuit of the slow-releasing relay 3| which on releasing disconnects master ground from the various circuits. This relay at its upper inner armature. and back contact, applies a release ground to release conductors |54 and 83 which energize the connector release magnet |35 and nnder release magnet 5|. These magnets, on operating, release the connector and the finder switches respectively, allowing them to return to their normal idle positions. In systems or this type it is frequently desir able that a called subscriber be provided with two or more lines so that in the event that the iirst one oi these lines is busy, a second or third will be available so that the subscriber can always be reached. This arrangement is commonly known as consecutive number hunting, since in originating a call, the calling subscriber will dial the number assigned to the called subscriber and in the event that that line is busy, the con nector will hunt over the remaining lines of a group assigned to the given subscriber until a line is found that is idle. To achieve this end, a vpermanern; ground is placed on the connector hunt multiple iâ-lä oi all numbers in the consecu tive group except the last. When the connector switch rests on the iirst number of the consecu tive group, ground is red from the multiple bank contact §35 through connector hunt brush S4, conductor §35, back contact and armature of re his receiver from its switch-hook, a direct cur lay 9d, conductor iS’i, baci; Contact and armature rent circuit is extended through the called sub 45 oi relay itil, to conductor |38. This ground is ex station B. This sets into operation the ringing tended to the busy delay relay m2 so that the trip circuit which may be described as follows: test may be made over the regular busy test An electron discharge device lle has been main circuit. In the event that the ñrst line in the tained in its non-conducting condition by means consecutive group is busy, the electron discharge of the negative bias supplied over potentiometer 50 device iíiâiwill not become conductive and thus £28 through resistor |29 to the control grid of relay le? will not be energized. rî‘he ground po this device. The alternating current voltage tential is applied from conductors |36 and |39 which exists across resistance |25 during the through the back contact and armature of the ringing period does not affect the bias of this connector secondary motor magnet lûíl through tube since the cathode ilgb and grid liga are 55 the winding oi the connector pulse assuring relay maintained at the same potential being coupled í?liì to negative battery. The operation of this re on an alternating current basis by condenser |39. lay lilo completes a circuit through its front con Thus, alternating voltage will not fire the tube. tact and armature, extending ground to the sec However, when direct current continuity is es ondary motor magnet ,thus advancing the tablished in the ringine circuit, as a result of 60 switch to the second line in the group. The con the subscriber answering as just described, a nector sleeve brush sli then rests on the second constant drop occurs across resistance |2li which line in the consecutive group and the busy test is is negative as it is applied to the cathode oi the again applied in the same manner as described ringing trip device H9. This in effect reduces previously. il" the second line in the group is also the bias on the ringing trip device and the de 65 busy, the relays illíl and Eile will operate to vice becomes conductive. The conducting cir gether in the pulse` assuring arrangement to ad cuit then extends from the grounded side of re vance the connector switch in its secondary mo sistance 52e through ringing trip device H9, con tion until either an idle line is found and out ductor itl, armature and front contact of relay through by the conventional busy test operation l, conductor 232, armature and back contact of 70 or if all the lines in the group are busy, ground relay S33, lower winding of ring trip relay |2I, no longer appears on connector hunt brush 94 to a positive source of voltage of the order of 150 and relay H32 will be deenergized to allow busy volts. When the ringing trip relay operates, it tone to be applied to the calling subscriber’s line. locks up to master ground at its uppermost arma Relay |37 operates to interrupt the operating ture and iront contact. At its inner armatures circuit of magnet ltdwhen an idle line is found. 12 _. 11 Frequently in systems of this type, the con nector is provided with a series of trunks lead _ . , , cold cathode arc discharged device 53 which lsl also used to stop the line finder in its secondary hunt motion. It will be recalled that as soon ing to a distant exchange. In such a system, as the master start ground is applied to the cir when a calling subscriber of the local exchange cuit by means of the group line relay 5, the al Ul wishes to reach a distant exchange he will dial a lotter stop relay I9 (Fig. 2) is energized. The single digit. In response to this single digit, the operation of this relay closes through a circuit connector will operate to effect its group selection extending from a positive source of voltage after which this connector will operate to hunt through variable resistance |10, front contact and for an idle trunk in the group selected. This is armature |1| of relay I9, conductor |12, to con accomplished in this system by extending a lead 10 denser |13, thence over conductor 1|, front con from one of the group multiples into all con tact and armature of relay |9, to ground. Re nectors in this office. In the connector circuit sistance |10 is adjusted so as to permit condenser under discussion, this is lead number |4| (Fig. |13 to charge slowly and so that the rise in po 3). Upon the completion of the series of tens tential appearing across this condenser will not impulse, ground is extended from master ground be sufficient to ñre arc discharge device 58, this in the connector through normally opened pri voltage being applied to starter anode 54 through mary off normal contacts 91, and the normally protective resistance |16 until sufficient time has closed secondary off normal contacts S3 through elapsed for the normal operation of the allotter back contact and armature of relay 14, conductor and the line finder. If this time is exceeded, |42 'to the connector brush 95. If the number 20 the ñring of the device 58 will cause the opera dialed brings the connector brush 95 into con tion of relay 20 as if the device had been ñred tact with lead |4|, the group is thus identified through current flowing in winding 48 in a nor as a trunk group and the hunting circuit is ener mal manner and the allotter will thus release. gized. This circuit extends from negative bat however, the allotter successfully completes its tery through the winding of relay |40, armature 25 If, operation, the charge of condenser |13 will be and back contact of magnet |00, lead |39, arma removed upon the release of relay I0, over the ture and back contact of relay |01, lead |31, path which can be traced from condenser |13 armature and front contact of relay 99, which through conductor |12, back contact and arma is in its operated condition, conductor |4|, con ture of relay |9, through resistor |18 and back to nector brush 95, conductor |42, armature and 30 condenser |13. back contact of relay 14, through the off normal In the event that the line finder goes to the contacts 91 and 98 to master ground. This sets overflow position due to failure of the allotter into operation the pulse assuring arrangement transfer relay 2| or some failure in the second of relay |40 and magnet |00 which act to ad ary motion circuit, the arrival at the overfiow vance the brushes in their secondary motion. As 35 position of the switch will close the overflow soon as the trunk group is reached, a circuit is contact |50 (Fig. 2) in the switch itself which completed for energizing relay |43. This cir will return a ground through allotter brush 5| cuit extends from negative battery through wind to the hunting lead 50 of the line finder. This ing of relay |43, make before break contact of pulse of ground will be transmitted through the this relay, conductor |14, lead |4|, connector 40 armature 49 and front contact of relay I9 and brush 95, lead |42, armature and hack Contact through the primary winding 48 of the trans -of relay 14, the off normal contacts 91 and 98, to former. The voltage induced in the secondary master ground. The operation of relay |43 acts winding 52 of the transformer initiates conduc to remove battery and ground respectively from _ tivity in the electron discharge device 58 which -relay |33 and to interconnect the windings of will again simulate the completion of the line this relay so that it becomes merely an imped finding operation. The allotter and line finder ance across the called trunk. This interconnect will be released as previously described and a ing path extends from lead |44 to relay |33, new link will be seized. through lead |45, armature and front contact of , This system is particularly adapted for use in relay 30, lead |46, armature and front contact of remote and unattended branch exchanges. relay |43, lead |41 to relay |33. The operation Therefore, adequate protective devices must be of relay |43 also extends ground through its incorporated therein so that extensive tie-up of armature and upper front contact, through lead service will not occur. Since the relays in the v|48 to energize the upper winding of relay |2|, allotter are common to all the links in the thus immediately tripping the ringing current 55 first systems, it is necessary to provide a secondary -and thereby preventing ringing current from go allotter which will function in the event of fail ure of the first. In order that this secondary allotter will not stand idle during functioning of the first allotter, the system is arranged so that 60 tion, contact 98 opens, thus interrupting the cir each will serve one-half of the lines and one-half cuit of relay 99. When this relay falls back, of the links in the system. A transfer circuit is ground is continued from multiple bank termi incorporated which will allow the lines served by nals opposite the connector hunt brush 94 and the first allotter to start the secondary allotter pulsing is completed in the same manner as in in the event of the failure of the first. If all the consecutive number hunting, the busy test be 65 links served by the first allotter are busy, a ground ing applied at each step. When an idle trunk is is extended through normally open off-normal found, the busy test device |03 becomes conduc ycontacts |5| (upper left in Fig. 2) in series of all tive and the talking connections are cut through links served by the first allotter, through the lower to the trunk in the conventional manner. winding of allotter start transfer relay |5, to 70 Several safety features have been employed in .negative side of battery. When this relay is ener the design of this system to protect the mecha gized, any master start ground which comes from nism and circuits from extensive tie-ups due to the group line relays, such as 5, which are ordi Yfailure of parts or dirty contacts in relays which Anarily served by the first allotter will be trans hinder'the closing through of circuits. One of ferred to the master start lead |52 (Fig. 1) of these features involves the use of the gas filled 75 ing out on the trunk. The switch now hunts in the secondary motion direction. As soon as the switch moves off normal in its secondary direc 2,409, 145 i4' the second allotter. Thus, the second allotter the line finding operation is also indicated by the will respond to signals from all the lines in the system. When any link served by iirst allotter operation of the cut-01T relay 6 of the calling line again becomes idle, allotter start transier relay i5 will be deenergized and will again allow signal» ling from the group line relays ordinarily 'served by the ñrst allotter to be transmitted into this allotter. if allotter start relay l5 is energized group served by the first allotter are waiting to be and. in the event that no other lines in that found, allotter failure relay |55 is deenergized and a discharging ground is returned to con denser |55 through the armature and back con tact of allotter failure relay |513. and a signal from any group line relay, such as 5 A modiiìed form of ringing trip arrangement ordinarily served by the first allotter, is tran-s 10 or trigger circuit which can be substituted for mitted into the second allotter, the operation of v that disclosed in Fig. 3, is shown in Fig. 6. in. the allotter start relay ES in the second allotter, this arrangement, the voltage on the starter an will complete its cycle of operation. This is ode |8| of the gas-filled arc discharge device eifected by a circuit extending from ground |35 is adjusted by means of the potentiometer through the lowermost armature and »front con 15 P, to be within a few volts of the iiring poten tacts of an allotter start relay similar to relay tial of the device. superimposed, interrupted i9 (at left of Fig. 2), conductor l d8, armature and ringing current is applied vto the called line front contact of the number one allotter start transfer relay i5, the lower winding of this relay. through resistor |2ê and condenser |86. During the ringing and silent periods the voltage drop to the negative side of the battery. This main 20 across condenser ißt is negligible and thus >the tains allotter start transfer relay |5 in number potential between the cathode |82 andstarter one allotter in its operated position until the com» anode its of the discharge device remains con pletion of the line finding operation and thus pre' vents this relay from being deenergized in case a link. ordinarily served by this allotter becomes idle during that hunting period of the iinder started by the number two allotter. stant. When, however, the hook-switch at the called substation is closed and direct current ñows in the line, a drop appears across resistor |24 and condenser |86, such that the cathode |82 of the discharge device becomes more negative. This As soon as a group line relay similar to relay 5 brings the device to firing potential and it be is energized, a circuit is closed which energizes comes conductive. The ring trip relay l2 lo. oper the allotter failure relay |55. The operation of 30 ates in series with the discharge device and acts this relay opens a contact which removes ground to disconnect the ringing current and to apply from the allotter failure circuit. This allows talking battery to the line in the manner simi condenser |55 to start charging through resistors lar to that shown in Fig. 3. |55 and iig. The charging circuit extends from a positive source of voltage, of the order of 150 volts, through the upper winding of the allotter start transfer relay i5, through resistors |79 and |56 to condenser |55, and ground. In the event of mechanical failure of certain relays in the allotter circuit or mechanical failure of the A further modified form oi trigger circuit is shown in Fig. 7 which differs from the trigger or ringing trip circuit of Fig. 3 in the specific manner in which the tripping Voltage is applied to the cathode H95 of the gas discharge device or Thyratron H9. In the arrangement of Fig. 40 7, the resistor 2% and the condenser I 31| con allotter motor magnet 85 (Fig. 2), the allotter stitutes a voltage divider. would not move to seize a new link and any rent flowing through resistor |24, the grid ||Sa subsequent calls would not be completed. The condenser |55 then charges through this circuit until the voltage on the starting anode |59 or" the electron discharge device itil (Fig. 1) becomes high enough to initiate conduction between the of the discharge device HS is biased by means of a potentiometer |23 so that the discharge de vice does not conduct. Alternating current may electrodes |52 and |63. ' When the electron dis~ time constant of the resistor 2S@ and the con With no direct cur also be passed through the resistor i213 and the discharge device still will not conduct, if the charge device becomes conductive, it energizes denser |3ß is greater than the period of the the allotter start transfer relay l5 through a cir 50 alternating current. When direct current iiows cuit which extends from a positive source of through the resistor iâß at the time when the voltage through the Lipper winding of this relay called partly answers by removing his receiver |5, key i6@ through the anode |62 and cathode from its switchhook, a drop appears across re itâ oi the electron discharge device ißt to ground. sistor iìil as a result of which the condenser |39 This acts to transfer the master start ground 55 is charged so that a negative voltage appears on which cornes from the group line relays ordi the cathode M927 of the discharge tube. The narily served the ñrst allotter to the master start lead |52 of the first allo‘tter. The allotter start transfer relay l5 remains operated until vacuum or gas rectifier 253|, as the case may be, in the cathode circuit ci the discharge device I I9, prevents the discharge of the condenser. Thev the circuit through the electron discharge device 60 mentioned negative voltage present at the cath |55 is broken at the manually operated key |54 ode ||9b efîectively reduces the bias on the dis by a repair man who is also signalled by the oper charge device ||9 causing it to conduct. The ation oi this device. The completion of the line rectifier tube âti now passes the plate current finding operation is indicated to the allotter fail of the discharge device HQ, in a circuit from ure circuit by the operation of the allotter control ground, through rectifier 2B |, cathode l I‘Bb, anode relay 2?; and by the allotter advance relay il' ||9c of the arc discharge device H9, lower wind which close a circuit from ground in series with ing of relay |2|a through armature |3341 of re the armatures and front contacts of these relays lay |33, to the positive source of high voltage. over the lead i‘l‘t through resistors |51 and |55 Ringing trip relay i2! becomes energized to dis to condenser |55. Condenser |55 is thus dis 70 connect the ringing current and to cut through charged through this path and prevents electron the connection from the calling line to the called discharge device |559 from operating, The time line. . interval allowed the line finder and allotter to Resistor |24 may be made quite low so that complete their operations is determined by the any circuit associated with this trigger circuit magnitude of resistor H9; The completion of 75 will not be appreciably affected thereby. Re»v :34,469,145 15 sistor 200 can be made quite high so thatV the minaL‘an arc discharge device having an anode, trigger circuit is of such impedance as to have a negligible effect on any associated circuit. If the present arrangement is used only to detect the presence of direct current and no al ternating current discrimination is desired, con denser l3ll« can be omitted. Resistor 282 is in serted to dampen any relaxation oscillation. It should be understood that the present dis closure is for the purpose of illustration only and 10 a cathode and a starter electrode enclosed in a gaseous atmosphere, a unidirectional source of electrical energy, a circuit including said source as well as said cathode, said anode and the gas eous atmosphere, whereby current ñows in said circuit when an arc discharge is initiated in said device, means for discharging said electrostatic charge responsive to the engagement of said switch with said terminal, and means responsive to said discharge for applying a starting poten » that this invention includes all modifications and tial to said starter electrode to eiîect arc dis equivalents which fall within the scope of the charge in said device, and means for stopping said appended claims. switch operated in response to current ñowing in What I claim is: l. The method of initiating electrical conduc 15 said circuit. 6. In a telephone system, a line having a ter tion through an arc discharge device having an minal, means for associating an electrostatic anode, a cathode and a starter electrode, said charge with said terminal when said line is to be cathode and said anode being connected in series selected, a movable switch for selecting such line, with a source of unidirectional electrical energy, which method comprises accumulating an elec 20 means for moving said switch to engage said ter minal, an arc discharge device having an anode, trostatic charge from a relative low voltage a cathode and a starter anode enclosed in a gas source, discharging said charge, utilizing said eous atmosphere, a unidirectional source of elec discharge to develop a voltage of a higher order, trical energy, a circuit including said source as applying said higher voltage to the starter elec well as said cathode, said anode and the gaseous trode to cause a discharge in said device. atmosphere, when an arc discharge is initiated 2. The method of initiating electrical conduc in said device, means for discharging said elec tion through an arc discharge device having an trostatic charge responsive to the engagement of anode, a cathode and a starter electrode, said said switch with said terminal, and means includ cathode and said anode being connected in series with a source of unidirectional electrical energy 30 ing a step-up transformer responsive to said dis charge for applying a starting voltage to said which method comprises accumulating an elec starter anode to effect arc discharge in said de trostatic charge from a relative low voltage vice, and means for stopping said switch oper source, discharging said charge, inductively uti ated in response to the arc discharge in said lizing said discharge to develop a voltage of a higher order, applying said higher voltage to the starter electrode to cause a discharge in said de device. ' 7. In a, telephone system, a telephone line com prising tip, ring and huntconductors, contacts in which said conductors respectively terminate, a switch having tip, ring and hunting brushes charge device responsive only to voltage of a 40 movable into engagement respectively with said tip, ring and hunt contacts, operating means for higher value, said arc discharge device compris moving said switch brushes into engagement with ing a cathode, an anode and a starter electrode vice. 3. In a low voltage arrangement for initiat ing electrical conduction through an arc dis enclosed in a gaseous atmosphere, a load unit and a source of unidirectionl current connected said contacts, a condenser and a resistor con ing varying current or“ relatively low voltage to flow through said primary winding. and a starter anode enclosed in a gaseous atmos nected in multiple, a circuit closed responsive to 45 the initiation of a call on said line, said circuit in series with said anode and said cathode, said including a battery as well as said tip and ring source having its positive and negative termi conductors in series with the multiple-connected nals respectively connected to said anode and resistor and condenser whereby said condenser said cathode, a step-up transformer having a becomes charged, said hunt contact being con primary winding and a secondary winding, said secondary winding being connected in circuit 50 nected to one terminal of said condenser, an arc discharge device including a cathode, an anode with said starter electrode, and means for caus phere, a stopping relay, a discharge circuit in cluding a source of unidirectional electrical energy 4. In a low voltage arrangement for initiating electrical conduction through an arc discharge 55 in series with said relay and also in series with said cathode and said anode as well as the space device responsive only to voltage of a higher value, therebetween, a step-up transformer having a said arc discharge device comprising a cathode. primary winding and a secondary winding, a _an anode and a starter electrode enclosed in a circuit including said secondary winding and said unidirectional current connected in series with 60 starter anode, a circuit including said primary winding, said hunting brush and said hunt ter said anode and said cathode, said source having minal and also said condenser whereby said con its positive and negative terminals respectively denser discharges through said primary winding, connected to said anode and said cathode, a step up transformer having a primary winding and a 65 and means including said relay for stopping said operating means. secondary winding, said secondary winding being 8. In a telephone system, a telephone line com connected in circuit with said starter electrode, prising tip, ring and an associated hunt conduc a condenser, means including a relatively- low tor, contacts in which said conductors respec voltage source of electrical energy for charging tively terminate, a switch having tip, ring and said condenser, and means for discharging said 70 hunting brushes movable into engagement re condenser through said primary winding. spectively with said tip, ring‘and hunt contacts, 5. In a telephone system, a line having a ter operating means for moving said switch brushes minal, means for associating an electrostatic into engagement with said contacts, overflow con charge with said terminal when said line is to be tacts closed as a result of a predetermined move selected, a movable switch for selecting such line, means for moving said switch to engage said ter 75 ment of said switch, a condenser and a resistor gaseous atmosphere, a load unit and a source of 42,409,145 17 18 >connected in multiple, a circuit closed responsive ageof such low vvalue applied thereto that it fails to render said device conducting when the cathode is connected with the line characterized Ato the initiation of a call on said line, said cir cuit including battery as well as said tip and ring conductors in series with the multiple-connected -resistor and condenser whereby said condenser becomes charged, said hunt contact being con as busy, and means controlled vby the conducting _condition of said device for indicating the idle condition of said line. 11. Ina telephone system, a line having Va terminal, means forv associating an electrostatic charge with said terminal when said line is to be selected, a movable switch for selecting such line, nected to one terminal of said condenser, an arc discharge device including a cathode, an anode 'and a starter anode enclosed in a gaseous atmos phere, a stopping relay, a discharge circuit in cluding a source of unidirectional electrical en lmeans for moving said switch to engage said ter ergy in series with said relayand also in series minal, an arc discharge device having an anode,.a with said cathode and said anode as well asv the cathode and a starter anode enclosed in a Igas eous atmosphere, a unidirectional source of elec fspace therebetween, a step-up transformer hav ing- a primary winding and a secondary winding, ' trical energy,l a >circuit including -said source i' as _a circuit including said secondary Vwinding and .said starter anode,ha circuit including said pri jwellfas said 'cathodajsaidfanode and the gaseous mary windingsaid hunting brush and said hunt îterminal and `also said condenser whereby said cuit vwhen an arc‘ discharge is initiated in said device, means, for discharging said electrostatic charge responsive to the engagement of ‘said switch with said terminal, means responsive to atmosphere, whereby current' ñows in saidcir condenser discharges through said primary wind- ~«ing, means responsive- to the closure of said over iiow contacts for transmitting current through Vsaid discharge for applying a starting' potential to said starter anode .to operate- said arc dis said primary winding whereby the discharge cir cuití isßclosed through said device, and means in cluding said relay for stopping said operating means. ` charge device„means including acondenser hav ing a delayed charging rate for applying a start ing potential to said starter anode after a pre determined'interval to effect arc discharge in said device, and means for rendering said con ‘ 9. In a telephone system, a group of telephone lines, each having a pair of talking conductors, a group relay common to said group of lines, said relay having one terminal of its winding con nected to one pole of battery and having its other terminal connectable in series with the talking conductors of any one of said lines on theini tiation of a call thereon, a hunt conductor for each line terminating in a hunt contact and'nor denser ineffective as aresultofthe normal oper ation of said arc discharge device in response-to the discharge of said electrostatic charge, and means for stopping said switch operated in re-> sponse to current flowing in said circuit. .. 12. In a ringing trio arrangement, a conductor having a source of alternating current superim mally connected to one of said talking conductors posed on. direct vcurrentconnect'ed thereto, said of its line, a condenser and a resistor each hav conductor` during a ñrst period being connected ing a pair of terminals, the first terminal of ina circuit continuous-only to alternating cur each pair being connected in common tov said rent and being connected'during a second period hunt conductor and the second terminal of each 40 ina second circuit continuous to direct current, pair being connected in common to the other a dischargedevice having a cathode, an anode pole of battery, whereby said conductor becomes and a control electrode, an anode circuit includ charged, a cut-off relay individual to each line ing said anode, Vsaidcatl'ioda-a ringing trip.re-. and eliective on operation to disconnect said group relay and to disconnect the hunt conduc lay and >also,afsource of current, meansfor biasf tor from said talking conductor, va switch for device does not conduct`.during saidñrst period, ing' said control electrode-tc a degree. that said seizing a line characterized by a charged con denser, said switch having brushes including a hunt brush movable into successive engagement with the hunt contacts of said lines, means for and means responsivefto-the flow of direct, cure. rent through said conductor duringlthe second , period .for rendering said> cathode `negative` with. moving said switch brushes, means responsive to the engagement of the hunt brush with the hunt contact connected to said charged condenser for respect l’tofit'sîcondition during said fñrst 'period' whereby .the bias. on ls'aidgde'vice is effectively re.-.¿. duced sô'th'at thedevice becomes conducting'an'd. thetrio rt-:la-y.-- operates. '_l.' '1`.. ’ ‘ causing said switchv to seize said line, and means " 13.' In @ringingtriparfaugement, a. conductor.. responsive to the seizure of said lineior operat-` CA' Ll having a source 'of alternating current superim-v ing the cut-oîî relay thereof. Y l 10. In a telephone system, a, line, means for characterizing said line as idle by a negative voltage of a given value and for characterizing , said line as busy by a negative voltage of a lesser (i i) value, a test circuit, an arc discharge device in cluded in said- circuit, said arc discharge device comprising a cathode, an anode and a starter anode enclosed in a gaseous atmosphere, a source of relative high positive voltage connected to said anode, means for connecting said cathode to said line, a voltage divider having its íiXed ter minals connected respectively to said anode and to said cathode and having its movable element connected to said starter anode, said movable ele ment being adjusted so that the starter anode has a starting voltage of such value applied there to that it renders said device conducting when said cathode is connected to the line when char acterized as idle but the starter anode has a volt posed o`n 'direct current' connected thereto, .said conductor duringT aiirst vperiod being connected in a circuit continuousonly to alternating cur rent and being _connected _during a second period in a second'circuit continuousto direct current, a resistor connected 'in' series with said conduc tor, a discharge device having a cathode, an anode and a control electrode, an anode circuit including said anode, said cathode, a ringing trip relay and also a relatively high voltage source of current, a second resistor and a condenser con nected in series and placed across the terminals of said first resistor, one terminal of the condenser being connected to the positive side of said direct current source, and a rectifier tube having a cathode and an anode, the anode of said rectifier being connected to the cathode of said device and the cathode of the rectiñer being connected to the positive side of said direct current source. 14. In a ringing trip arrangement, a wanted 2,409,145 19 telephone line, a conductor, a source of ringing current, a ringing trip relay for controlling the connection of said source of ringing currentlto said conductor, means for connecting said con ductor to said wanted telephone line in the course of extending a telephone call to said line whereby said line is signalled, an electron discharge device 20 of alternating current through said second resis tor. 17, In an arrangement for initiating electrical conduction through a discharge path, a discharge device including a cathode together with an anode constituting said discharge path, said device also including a control electrode, means normally biasing said control electrode to a value whereby having at least a cathode, and an anode, .an said device does not discharge, a network com anode circuit including said anode, said ringing trip relay and a source of current, means respon 10 prising a capacitor and a resistor together having a period or time constant of a given value, a sive to the answering of the signal on the wanted source of alternating current of shorter period line for causing said discharge 4device to pass than that of said network, a source of direct cur suñîcient current to operate .said >relay whereby the source of ringing current is disconnected from rent, a second resistor through which either said said wanted line. alternating current or said direct current can be , 15. In a ringing trip arrangement, .a wanted _telephone line, a conductor, a >source of ringing current, a ringing trip relay for controlling the caused to ñow, ,means for applying to said net work the drop across said second resistor due to direct current flow therethrough whereby said capacitor is charged, vmeans for connecting the connection of said source of ringing current to said conductor, means for _connecting said con zO negative terminal of said capacitor to said cathode, a cathode circuit connected to said ductor to said wanted telephone line in the course cathode, anda rectiñer .connected in said cathode of. extending a telephone call> to said line whereby circuit to prevent unwanted discharge of said said line is signalled, an electron discharge de vice Vhaving a cathode, a control electrode and an Y anode, an anode circuit including said cathode, said anode, said ringing trip relay and a source of current, means for applying a bias to said control electrode whereby said device vdoes not pass current, means responsive to the answering of the signal on the wanted line for overcoming said bias whereby said discharge device passes suñicient current to operate said relay thereby disconnecting the ringing current from said wanted line. , , 16. In an arrangement for vdiscriminating be tween the ñow of alternating current and direct current in a given circuit, a discharge device in cluding a cathode together `with an anode con capacitor. 18. In an arrangement for initiating electrical conduction through a discharge path, a discharge device including a cathode together with an anode constituting said discharge path, said device also including a control electrode, means normally biasing said control electrode to a value whereby said device does not conduct, a cathode circuit connected to said cathode, and means for apply ing a negative potentia1 to said cathode whereby the bias applied to said device is effectively re duced and it becomes conducting. 19. In an arrangement for initiating electrical conduction through a discharge path, a discharge device including a cathode together with an anode constituting said discharge path, said device also stituting an electric discharge path, said device also including a control electrode,> meansv nor 40 including a control electrode, means normally biasing said control electrode to a value whereby mally biasing said control electrode to a value said device does not conduct, a cathode circuit whereby said device does not discharge, a net connected to said cathode, a rectiñer connected work comprising a capacitor and a resistor to in said cathode circuit, and means for applying gether having a period or time constant ,of a given value, asource of alternating current- of shorter ï a negative potential to said cathode whereby the bias applied to said device is eiîectively reduced period than that of said network and a source of and it becomes conducting. direct current to be discriminated, a second .re 20. In an arrangement for initiating electrical sistor connected in saidcircuit through .which conduction through a discharge path, a discharge either said alternating current or said direct cur-f rent can be caused to now, means for applying - to said network the ydrop across said second resis tor due to direct current flow.. therethrough whereby said capacitor is charged, means for device including a cathode together with an anode constituting said discharge path, said device also to said cathode, a rectiñer connected in said cathode circuit ,to prevent unwanted discharge of said capacitor, a relay connected in said dis charge path to be `operated by the electric dis charge therethrough, and means responsive to including a control electrode, means normally biasing said control electrode to a value whereby said device does not conduct, a cathode circuit connected to said cathode, an anode circuit con nected to said anode, a rectiñer connected in said cathode circuit and connected to said anode cir cuit, and means for applying a negative potential to said cathode whereby the Abias applied to said device is effectively reduced and it becomes con the operation of said relay for stopping the flow ducting. connecting the negative terminal of said capaci tor to said cathode, a cathode _circuit connected FRANK A. MORRIS.