Патент USA US2107817код для вставки
Feb. 8, 1938. J, |, DAVls 2,107,817 INTER-OFFICE COMMUNI CATION SYSTEM Filed Jan. 29, 1955 -3 Sheets-Sheet l I//6" Feb. 8, 1938. J. |. DAVIS 2,107,817 INTER-OFFICE COMMUNICATION SYSTEM Filed Jan. 29, 1956 3 Sheets-Sheet 2 jay Z15; ,Feb. 8, 1938.‘ _ J. l. DAVIS 2,107,817 INTER-OFFICE COMMUNICATION SYSTEM Filed Jan. 29, 1936 s Sheets-Sheet s ATTORNEY3. Patented Feb. 8, 193a _ " ‘UNITED STATES _ 2,107,817 PATENT ' OFFICE 2,107,817 a . INTER-OFFICE COMMUNICATION SYSTE Jack I. Davis, Chicago, Ill., assignor to Sidney Ludwig, Chicago, Ill. ‘ Application January 29,1936, Serial No. 61,418 4 Claims. (01. 179-37) This invention relates to an inter-office com munication system, and more particularly to a system wherein a plurality of units in different parts of the o?ice are connected by a cable. One feature of this invention is that it results in better quality of received speaking; another feature of this invention is that it avoids cross talk between different lines in the same cable; yet another feature of this invention is that it [0 enables a visual indication of the party calling another, over the same cable wire as the voice transmission; still another featureof this inven tion is its simplicity of installation; another fea ture of this invention is the ease with which addi The main cable and feeder cables are of low im pedance, and the amplified output of the micro phone is transmitted through the cable, the line impedance being substantially reached at each end of the transformer. _ 5 Referring more particularly to Fig. 1, each unit, adapted to be placed on a desk, contains a micro phone III or other means for translating sound waves into electrical energy, an amplifying sys— tem for the output of the microphone, indicated 10 here in general by the numeral H, a speaker in dicated in' general as I2, a power pack iii, an in dicator l4, and the necessary switches. A feeder cable l5 connects to the main cable i6, to which [5 tional units may be connected to those already in , are also connected other desk units l1, I8, and stalled; a further feature of this invention is that Hi. It is to be understood that the number of it may be operated entirely from the commercial wires contained in the main cable and feeder cable are covered by the number of units which source of alternating current; still another fea ture of this invention is that it may be used as a it is desired to use, in each case being one more conference communication system; other features than that number. The microphone Iii is preferably of the carbon and advantages of this invention will be apparent from the following speci?cation and the drawings, button type,__although it may be a ribbon type or any other in general use. ' Its output is passed in which Fig. l is a schematic diagram showing such a through the primary of the transformer 20, power 25 system, one unit being shown in detail; Fig. 2 for it being supplied from the power pack- i3 - illustrates the manner of connecting the various through the line 2i, a ?lter system comprising units by cable; Fig. 3 is a diagrammatic view of resistors 22 and 23, radio frequency choke coil 24, one of- the three-way socket-elements used for and condenser 25. The voltage developed in the connection; and Fig. 4 is a front elevation of a secondary of the transformer 20 is applied through the volume control 26 to the grid of the 30 preferred form of unit. . Modern inter-office communication systems of triode tube 21. The cathode 28 of this tube is grounded through the bias resistor 29, shunted by the type designed for use by executives particu larly are subject to many disadvantages. The the condenser 30. The heater 3| is supplied with majority of these systems comprise a unit for a current by the secondary 32 of the power pack. 35 desk including a microphone and‘ a speaker, and . The plate 33 of this tube is connected to the grid having switch means for connecting it with any 34 of the pentode tube 35 through a resistance chosen unit in the system. As now designed, most of these transmit the microphone output through the cable or other connecting network to the 40 other unit, and shielded connections are necessary to prevent cross-talk and other interference. Most of these systems also necessitate additional wires to transmit current to operate an indicat ing device. The installations are expensive, and 45 di?icult to change or to provide for the addition of other units. _ The present invention comprises an inter-office communication system having a plurality of desk . units each having a microphone,’ a vacuum tube 50" ampli?er for the output of the microphone, a it speaker, an indicating device, switches, and a 1. power pack ‘to enable operation from commercial alternating current. A single cable, containing only one more wire than the number of units is 55 connected to each of the units by a feeder cable. 15 . 2 25 30 35 coupling network comprising resistors 36, 31, 38, and 39 and coupling'condensers 40, ll and 42. The cathode 43 of the pentode tube 35 also has a. biasing resistor 44 in series therewith, shunted 40 by a condenser 45. The heater 56 is also sup plied with current from the secondary 32 in the power pack l3. It also has connected thereto the suppressor or grid 46. The output of the tube from the plate 46 is passed through the switch 45' 48 and shunted to ground by the condenser 49, and the primary of the transformer 50. This trans former is inserted in order to match the output impedance of the tube substantially with the line or cable impedance, and the switch 43 is pro- 50 vided so that when it is desired to talk to more than one of the other units, the switch ‘may be changed in order to match the output impedance more nearly to the impedance of several units in parallel. > 55 ‘ 9,107,817 The output of the line-matching transformer 50 is connected to a bus wire 5| to which are con _nected the contact points 52 of a number of switches, of which three are here shownas 53, 54, and 55. Direct current power, supplied by the power pack I3, is drawn from the lead 2| through the resistor 58 and the resistors,“ to the switch points 60 of the switches 53, 54 and 55. The points ii are the 011 positions of the switches. 10 The resistors 59 would be the same for each of the switches in a given unit, but would be different in each-unit. Thus the direct current ?owing from the unit when any switch is on the point 60 would .15 means here shown as a relay energizing coil 83 which‘ opens the contacts between 64 and 65; the voice modulated alternating current from the ampli?er of'the unit ill, on the other hand, passes through the operating coil 61 and energizes the speaker l2. It will be noted that‘ the speaker in each unit has no connection with the ampli?er of that unit; on the other hand, the operating current supplied to the speaker of a unit-qis in each case developed by the ampli?er in another unit and transmitted through the low impedance for each switch. cable to the speaker. - ‘ wire or lead 62 which branches it in one case to the indicator H, in series with the operating coil 20 63 of a relay having an armature 64 making con tact with the point 65, and in the other case to the armature 64. This armature is, normally maintained in contact with the point 55 by a spring 66. The voice coil 61 of the speaker I 2 25 is connected from 65 to ground. Thus when the - speaker I2 is inserted in the output of the tube 20 69 as a, load, and is shunted ‘to ground by con- > densers ‘l2 and 13 to make a ?lter network for the output of the recti?er. A switch 14 is pro vided to control the alternating current inputto the transformer 68. . ' tions between units may be seen more clearly by v mitted through the main and feeder cables, ener reference to Fig. 5, which illustrates schemati electric energy into audible waves. _ __The indicator II is essentially an ammeter, chosen with a range such that each of the re sistors 59 heretofore mentioned causes the needle of the indicator to stop at a di?’erent position on the face thereof, as'may be more readily seen from Fig. 4. That is, if the operator of the unit shown in detail in Fig. 1 wishes to speak to the , unit l8, he would ?rst throw his switch 53 to the contact 60, which would send a direct current through the cable to the indicator in the unit I8. This direct current would energize the relay coil in that unit and cause the contacts to break, thus opening the circuit through the speaker‘ voice coil 61. The indicator needle would swing to a position governed by the value of the resistor 59, and would in this case take the ?rst position to show that unit No. 1 was calling. As soon as the unit l8 has answered, the operator of unit No. 1 would throw switch 53 on over to point 52, where 50 upon the spring connected to the relay armature would restore connection to the speakei of. unit 18, and communication would be carried on. It is also contemplated that a small light or other indicating device might be used in series 55 with the indicator II to more readily call atten tion to the fact that one is being called over the system. ‘ Referring again to Fig. 1, the process willbe described when the‘ operator of the unit 18 an 60 swers the unit shown diagrammatically in Fig. 1. When the operator of l8 was signalled by the closing of the :switch53 the current travelled along the line or lead 85 between the contact points 86 and 81 of the plugs 80 (through the_ 65 intermediary of the three-way‘ socket element shown diagrammatically in Fig. 3 but not shown in ‘Fig. 1) and along the wire 88 of the main cable IE to the unit It; when the operator of the unit l8 answers, throwing his number 1 switch 70 would send current through the wire 89 of the main cable l5, across the contact points 90 and 9| (again through a three-way socket element not shown here), and through the wire 62 in the cable l5 to the speaker unit l2. In this con nection it will be noted that when the switch is 15 The power pack‘ indicated in general as l3 comprises a transformer 68 and a full switch rectifying tube‘ 59. The heater ‘Ill is operated from the secondary 51. The ?eld coil ‘H of the armature G4 is contacting 65, the ampli?ed out put of. the microphone of another unit, trans gizes the speaker and results in translation of the is relay coil 61 through the speaker l2 by blocking be diiferent for each unit. ‘ BI is the off position The input to each unit, transmitted through the cable from some other unit, is through the so set at signalling position and direct current is used it is prevented from passing through the The cabling arrangement and inter-connec 25 cally this invention as embodied in an inter- ' o?ice communication system comprising four units, each of these units being identical with that shown in detailin Fig. 1, the cabling corre sponding to that shown in Figs. 2 and 3. Each of the fourv units has a feeder cable connecting. to the main cable at a junction box or three-way socket illustrated in dotted lines in Fig. 5, shown in more detail in Figs. 2 and 3. Referring to Fig. 3 of the drawings, a schematic layout of each three-way socket shows that it merely. has one female member 15 for the reception of three. 40 separate plugs. By the use of these three-way ‘sockets each feeder cable from each unit may be attached to the desired wires in the main cable without splicing or soldering and similar addi tional units may be added,~up to the limit of the number of. wires in the main cable. Referring again to Fig. 5, the operative con nections and circuits between units will be more fully described. Inasmuch as the schematic illustration in this ?gure shows the device ‘em bodied only in connection with four units rather than with the five unit system shown in Fig. 1, the parts will be indicated by new reference nu merals. It will be understood,‘ of course, that each unit is similar to that described in com plete detail and illustrated in Fig. 1, in that it 65 contains a microphone, an ampli?er, a speaker, an indicator, and control switches. The addition ' of more units would merely necessitate the addi tion of further switches and further wires in the 60 cable, the switches always being one less than the number of units and the wires in the cable one more than the number of units. The left hand unit illustrated in Fig. 5, and here referred to as llll, is shown connected to the third unit I03. That is, unit IM has its switch marked 3 set in the talking position; and unit I03 has its switch marked I set in the talk ing position. Thus any sound input to the mi-' crophone I05 is transmitted through the lead I 06, the switch 3, the wire I01 and the relay I08 to the speaker I09 of unit 103. - Similarly, any sound input to the microphone I I0 is transmitted through the switch I and the wire III to the speaker “2 of the ?rst unit. The return cir 2,101,817 cuit in each case is made through the ground wire H3 common to all of the units. Circuits are thus formed with a minimum of wires en nbling units I and 3 to talk to each other, the‘ circuits being distinct so that the users may talk simultaneously, break in, or in any other way they desire. ' ‘ Similarly,v units I02 and I04 are shown with their switches in such position that they may 3 necting another unit to the main cable by a feeder. Fig. 3 is a schematic diagram of one of the socket-elements ‘ll, and-illustrates how the sockets are connected. It will be noted that each socket is provided, in addition to the holes ‘I! into which corresponding pins on the plugs 00 fit, with a recess ll adapted to receive a corre sponding key on the plugs 00. Thus. the various plugs, whether on the sections or portions of the main cable or on the feeder cables, must always 10 '10 talk -to each other at the same time that conver sation is going on between units iii and I03 with ‘be inserted in the proper way in the socket no interference. Switch No. 4 of. the second unit members ‘II. 'When it is desired to install an is set in the talking position, so that a circuit is inter-o?lce system of the type described herein, completed from its ampli?er through the wire it is not necessary to buy and install at one time “4 to the speaker of unit 104. This last men the full number of units which it is contemplated tioned unit has its second switch in talking posi using. The main cable is chosen to have a tion, so that a circuit from its ampli?er is com number of wires one more than the number of pleted to the speaker of unit I02 through the units which it is contemplated will eventually be wire H5. installed. The system may then be started with As heretofore described, not only may pairs only two or three units, if that be desired. Addi 20 of units talk independently of each other, but tional units, up to the limit of the capacity of any number of units may sit in what might‘ be the cable, can be added at any time by merely called conference arrangement. That is, it purchasing additional sections of. cable and addi would only be necessary for unit l0l to throw all tional socket elements and plugging them into three of his switches to the talking position to the already operating portion of the system. 25 supply the output of. his ampli?er to each of the As was heretofore mentioned, this system may other. speakers. Thus the user of the ?rst unit - beused to speak to one other unit or several other units at once. When only one unit is being could speak into microphone I05 and be heard simultaneously by the users of each of the other three units. If desired, any of the other units could throw a multiplicity of their switches in the talking position and answer the ?rst speaker, there the last user's voice being reproduced in such speakers as he chooses by the throwing of switches. - Referring again to Fig. 1, it will be noted that the operating coil 63 of the relay is in parallel with the voice coil 51 of the speaker i2. This condition does not prevent operation of the 40 speaker, however, since the impedance of a voice coil, usually only a few turns of wire, is very low compared to the impedance of the relay winding to currents of.,voice frequency. While such relay winding has a relatively low current 45 resistance, and thus enables easy operation of the indicator 14, it has an alternating current impedance many times that of the voice coil, and thus the major portion of power of an alternating current would be developed in the speaker rather 50 than being shunted out through this relay wind ing_ . , The values of the resistors and condensers heretofore described are chosen in accordance ' with the particular tubes and circuit employed, 65 and may vary considerably. In the particular embodiment of this invention disclosed in Fig. 1, tubes 21 and 35 are models F5 and F6 respectively, and the rectifier 69 is a Z‘. With these tubes, and the particular circuit disclosed, the follow 60 ing values were used: the volume control 26 was 200,000 ohms; resistors 22 and 23, 20,000 ohms and 10,000 ohms respectively; resistor 29, 2,500 ‘ ohms; resistor 44, 400 ohms; resistors 36, 31, 38 and 39, 75,000 ohms, 25,000 ohms, 250,000 ohms 65 and 50,000 ohms, respectively. Condensers 25 and 30 were 2 mi. each; condensers 4i and 42, spoken to, the switch 48 would be in the position illustrated in Fig. 1; when speaking to several 80 other units at once, the switch would be thrown to its other position in order to more nearly match the impedance of the speakers of the other units in parallel. In this connection it is to be understood that “speaker” is used to cover the 35 actual sound-producing device and its associated parts, including, for example, a matching trans former. Inasmuch as the output of the trans former 50 is placed on the bus bar or bus wire 5|, any number of switches may have the out put directed therethrough at once, up to the limit of the number of switches on the unit. When the word "number” is hereafter used in the claims, it will be understood that it means any number of units from one up to the total num ber of units in the system. While I have shown and described certain em bodiments of my invention, it is to be understood that it is capable of many modi?cations. Changes, therefore, in the construction and ar rangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims, in which it is my inten tion to claim all novelty inherent in the invention 65 as broadly as permissible, in view of the prior art. What I claim as new and desire to obtain by Letters Patent is: , 1. An inter-omce communication system of the character described, including: a plurality of units, each unit comprising a speaker, a micro phone, tube means for amplifying the output of said microphone, and an indicator; a cable con necting said units, said cable having therein only one more wire than the number of units; a source 65 of direct current associated with each of said units; and a‘ relay breaking‘ the circuit to said £1,- mf. each; condenser 40, .01 mf.; condenser 45, 10 mf.; condensers 12 and 13, 8 mi. each; and speaker when said indicator is being energized condenser 49, .02 mf. by direct current.‘ " 70 Referring more particularly to Figs. 2 and 3, the main cable, feeder cables, and three-way socket-elements 15 will be described. The main cable l6 comprises a number of sections, as 16, 11, and 18, between the various socket-elements 15. 75 Each socket-element provides a means of con ~ 2. An inter-office communication system of the character described, including: a plurality 70 of units, each unit comprising a microphone, tube means directly connected thereto for ampli fying the output of said microphone, a trans former for coupling said tube to a low impedance 75 4 ‘2,107,817 output circuit, a speaker, and switch means; and is adapted to energize the speakers of any num a cable connecting said units, said_ cable and ber of said other units. switch means being so constructed and arranged . 4. A unit adapted to be’ connected to any num- ' ' that said cable may be connected to the trans former of each unit to form a part of thelow ber‘oi' other similar units by a cable including only one more wire than the number 01' units impedance output circuit for transferring energy ‘to form an inter-o?‘ice communication system of to any number of the speakers ‘01' the other of said units. _units, each unit comprising a microphone, tube 3. A unit adapted to be connected to any num- means directly connected thereto for amplifying 10 ber of other similar units by ‘a cable to form an inter-office communication system, including‘: a speaker: a microphone; an amplifier directly connected‘ thereto and comprising ‘tube >means for amplifying the output of said microphone; 15 and a transformer‘ for coupling said tube means to a low impedancecircuit including said cable, whereby the output of the amplifier of said unit the character described, including: a plurality of _ the‘output‘of saidmicrophone; switch means; 10 .an indicator; and means permitting energiza tion or said indicator without energization 0! said speaker, through the same pair of wires in said cable effecting energization oi.’ said speaker, as a result of the operation of the switch means of 1‘ any of said other units. - . JACK I. DAVIS.