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Патент USA US3033951

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May 8, 1962
3,033,941 »
Filed July 14, 1958
2 .'Sheets--Shee‘tI 1
May 8, 1962
Filed July 14, 1958
2 Sheets-Sheet 2
Patented May s, i962x
apparent as soon as the call receiver acquired the habit
of disconnecting his bell circuit would be the avoidance
Robert R. Bell, 606 W. Wisconsin Ave., and Cari O.
Bì‘iend, 3073 S. Chase Ave., both of Niilwaukee, Wis.
of the all too frequent embarrassing telephone question
situation. Frequently, a call-receiver is not at liberty to
speak openly in the presence of others. With the bell
ringing circuit disconnected, the chance of a call from a
call-initiator having questions best answered at a time
Our invention relates to a new and novel means for
when the call receiver is alone is decreased, because the
altering the operation of telephones to thereby increase
call-initiator could force himself on the call-receiver only
their etfectiveness.
10 if his telephone was equipped with a circuit restoring de
Filed July 14, 1958, Ser. No. 748,259
9 Claims. (Cl. 179-89)
The telephone today has become virtually a necessity
vice, and then only with the full knowledge that the call-`
as a means of communication, particularly in business
restorer has someone with him or is otherwise preoc
and industry. The usual manner of signaling the person
called or call-receiver frequently becomes an intrusion of
Perhaps the greatest advantage resulting from use of
our system is one which is manifested less openly but
which actually results in a greater bene‘lit to telephone
phone calls. To entrust this matter to the discretion of
users. This benelit is the indirect creation of greater over
another person such as a secretary is not always satis
all -business etiiciency due to improved useage of the tele
factory however. Frequently, the person initiating the
phone. The telephone is a very etlic'ient and money
telephone call or call-initiator is capable of deciding 20 saving business device when used intelligently but it can
whether answering the call would be regarded as essential.
be a nuisance and crutch if used indiscriminately. Since
Our system permits a call-receiver to alter at will the
`our system indicates to the call-initiator the relative avail-v
normal signaling of his telephone so that, while so altered,
ability of the call receiver, the call-initiator is guided in
he will receive no calling signals such as the conven
his demands upon the call-receiver. With a decreased
tional ringing bell, but instead will receive a signal only 25 demand on the call-receiver’s time, he is able to devote
if the call-initiator decides that his message is truly im
more of his time to productive activity.
portant enough to warrant an interruption While the
Accordingly, a primary obect of our invention is the
call-receiver’s telephone is so altered, the call-initiator
provision of an apparatus for altering the operation of
will hear a special and distinctive signal indicating that
telephones that when desired, can eliminate all but abso
privacy and busy people such as business executives may
wish that they could eliminate all but truly essential tele
the call-receiver does not Wish to be intruded upon un
less it is absolutely essential. If the telephone of the call
initiator is equipped with a suitable complementary de- ~
vice, the call-initiator can then decide Whether to trans
mit the special signal which will cause the call-receiver
lutely essential calls.
Another object is the provision of an altered telephonex
system which permits a call-initiator to be apprised of the
fact that the person called does not wish to be interrupted
except for absolutely essential calls.
to be signaled. Call-initiators having telephones not so 35
Another object is the provision of an altered telephonev
equipped would be unable to intrude until the call-receiver
system whereby a call-initiator who receives an indication
restores normal telephone operation.
that the call-receiver does not wish to be disturbed at this
With our device, telephones may be altered in such a
time except for essential calls may nonetheless break>
manner that busy people are permitted to work without
through the call shutout if his instrument is equipped
undesired interruptions, but at the same time, are able
with a suitable complementary device for interrupting
to receive essential incoming calls. Our device eliminates
the shutout imposed by the call-receiver.
the discretion of a third party, such as a secretary, in put
Another object is the provision of a telephone system
ting through essential telephone calls and substitutes the
in which a call-receiver’s signaling device may be dis
discretion of the caller who may often be in the position
connected at will by the call-receiver for periods up to
to know whether or not his call is essential. Our device
andbeyond one hour,
also eliminates the inconvenience to others, as well as'
Another object is the provision of a novel telephone
the call-initiator, caused by the absence of a secretary
system in which a circuit, such as a bell ringing circuit,
who may be away from her desk for a variety of reasons
may be disconnected for periods of time up to one hour
by informing the call-initiator of his inability to put his
or more by means of a timing device.
call through. In other words, the call-initiator need not 50
Another object is the provision of a novel timer for
keep trying the call with consequent demands on the time
maintaining a circuit, such as a bell ringing circuit, dis
of other persons because he is informed that the call
connected based upon a capacitor discharge principle
receiver does not wish to be disturbed at that particular
whereby disconnections for periods of time up to one
time and the reason is immaterial.
Some of the above mentioned advantages would be of 55
immediate benelit upon installation of the system in ex-_
hour or more may be maintained.
Yet another object of our invention is the provision
of a restoring circuit which will permit a call-initiator hav
isting circuits. With the passing of time and the famil
ing a suitably equipped telephone to break vthrought-he
iarity acquired through use of the system, even greaterl
call shutout set up by the call-receiver, and will autoadvantages would accrue. For example, repeated use of
matically restore the shutout at the end of the call.
circuits embodying our device which would induce brevity 60
Gur invention is illustrated more or less diagrammati
of conversations because repeated calls by a call-initiator
cally in the accompanying drawings, wherein:
to a call-receiver having a telephone equipped with our
system would tend to indicate the relative activity at the
Y FIGURE 1 is a block schematic diagram of a system
for altering a call-receiver telephone circuit to preclude
call-receiving end of the line. Further, unessential calls
reception of all calls except those emanating from a tele
would be actually deferred because if the call-initiator is 65 phone equipped with a circuit interruptor;
aware of the fact that the call receiver is extremely busy
FIGURE 2 is a modification of the system shown in
at the moment, he will drop calls that actually need not
FIGURE l wherein certain functions have been com
be made or could be easily made at a later time. In
bined in order to simplify the circuitry and take advantage
addition, there will be less telephone tie-up from busy
of component parts; and
lines with a corresponding increase in telephone avail 70 FIGURE 3 is a detailed schematic diagram of the cir
cuits used in the system illustrated in FIGURES l and 2.
Another very practical advantage which would become
Referring now to FIGURE l, one method of implement
Unit b might be a suitable relay circuit actuated by
ing our inventioniszshown in block form. A-standard tele
phone instrument having a conventional bell signaling
circuit‘has’ been' m'odiñed so as to bring one of the bell’
the incoming ringing signal and could include provisions
for holding the relay during standard intervals between
ringing pulses. A ñve second delay should be adequate
wires Yrout through the connecting cord, the other bell
for example.
wire being ,connected within the instrument to a line wire,
R'; lFor purposes of clarity 'and description, we have
The distinctive busy-signal generator unit f could con
sist of any apparatus capable of ytransmitting a distinctive
indicated some lines with lettersrwhich may correspond
to colors. For example, Y would be yellow, G green,
tone or signal over the‘line. For example, we might
employ an electronic oscillator capable of generating a
R‘ red and O orange. `The incoming telephone line' G is;
connected‘to a switch A which may break the'telep'hon‘e' 10 tone of suñicient strength to be readily heard by the
calling party, and this tone might even be interrupted at
bell‘circuit' at AN, leaving’ the telephone line Wires G, R,
a rate of two or three times per second in order to give
connected: tothe instrumenh'and simultaneously connect'
the effect of the well known busy-signal. The pitch of
theVA bell circuit to contact AA, and the telephone line
wire G, to the‘contac't designated BA.
the tone should diíter from the standard busy-signal so
,thatV it is readily distinguishable. VThis signal is coupled
For- example, switch A-B could be a toggleV switch,
to the line in a manner which' does not draw DLC. from
ajlever switch, or a remotely controlled-relay which could
beî controlled by a timer controlled switching device, con
the line or Votherwise act` to bridge the line in such a
tained in a‘box Vand indicated in the drawings diagram
Way to actuate the “ring-cut-oif’"relay at the telephone
central oflice; This. assures that the ringing signal will
maticallyes unit'` a.
When> switch A-B is in the position shownand a 20 continue to be received and can be used to actuate the
local telephone bell or other signaling device if the special
ringing signal is‘received over the incoming. line, the
instrument bell‘doesnot ring, but instead a` ringing sig
“remote-ring” signal is received by unit e. The entire ap
paratus could be made'to function equally well if the ring
nal sensing unitV b, actuates a ring’relay switch Q making
cut-oi`f relay had been actuated, but this wouldv then
v contact‘at-'QA which turns on a distinctive busy~signalgenerator unit f. This distinctive signal is fed back into 25 require an additional suitable power circuit with which to
aetuate the localV telephone' bell when reconnected by
_theline through contact BAYto indicate that the receivingV
party’sf-_tcle'phone-’bell‘for signaling deviceîhas been dis-`
unit e, and a4 revision of the relay holding circuit in
unitV b.
connected because he“ doesv not wish to be> disturbed un
The remote-ring incoming-signal sensing-unit e senses
less'vitïislabsolutely essential; ln this case, the calling
party' must' have an instrument equipped with a remote 30 the signaling circuit; restoring signal generated by the
ring signal generator'unit g'with which he can generate.v _ caller’s unit g when the call-initiator wishes to interrupt
and send'a'signal which -will vbe received by unit efto `there
by~ close contacts AB `and'ABA tov restore the bellïcirc’uiti
the call-receiver; The nature of this signal is circum
scrìbed andfdeterminedby the parameters and character
istics of the telephone’ line and'the related equipment. A
Unity e` is’ al remote-ring-incomirig-signal sensing circuit.
During the time that the bell in the baseV of the tele; 35 major requirement is that unit e mustV not be actuated
phone? instrument 10 has beeny disconnected, the ringing
by'thev effects of thev standard ringing signal or by speak
signallha's. continuedïitobe received because the line has
' ing, shouting, Whistling, etc., into the telephone of the
callainitiator, or byv random line noise or switching
transients'. Conversely, unit e must be actuated only by
effectively' bridged in a manner equivalent to
“answering” the telephone, and, therefore, the ring-cut#
off-trelay atïthe'centraloñicehas not been actuated. Con 40 a special signal generated by the remote-ring signal gen
erator unit- g. Consequently, the special signal should
sequently,ïif« the callèiniti’ator’s telephone is equipped with
not resemble the regular’ringing signal or normal voice
av remote' ring signal generator unit g, which- has' been
frequencies or sounds which could' be emitted by the
actuated; the conventional ringing signal now operates
the’bell inthe telephone lil, and' if the receiving party
call-initiator'. For this reason, we have used frequencies
is present- he canv answer' theïtelephone in the normal 45 near'the- upper-most limits of the range of frequencies
manner. Answering the telephone bridges the line with
transmitted by the usual telephone circuits without undue
a' low! impedance which actuates> the ring-cutloíî relay
attention.> Frequencies on the order of 2500 to 2800
cycles' are satisfactory though they need not be restricted
in‘theicentral office and the bell thereupon stops-ringing.
This-is sensed by‘unit-` b which disconnects'l the remainder
to such a range.
To minimize the eiîects of random line noise and’switch
Vof the apparatus to await the next call.
, Our systemV will function on= the succeeding call inex~
ing transients upon unit e, as well as to minimize the
eiïeots of sounds transmitted by> the mouthpiece >of the
call-initiator, we have found it desirable to restrict the
band' of frequencies introduced into unit e by means of
During this time, the'receivingfpa’rty’can' also makeout'
goingî calls inv the' normal manner without' laltering the 55 a band-pass filter, or peaking coil or’resonant circuit.
actlyf theisame- manner providedtswitch A remains thrownl
to: contact
functions of the> telephone.
Since «even theV random line noise in this limitedL range
Diagrammatically represented at g is.v ay remote-ring
of frequencies in the “pass-band”'can have an equivalent
signalgenerator unit. This generator is actuated by- push
effective'value of .l volt R.M.S. or more, we have found
it desirable to limit the sensitivity’ of unit e to require at
button PB which reactivates the signaling'circuit of the'4
calllreceiver. Thus, when al call-initiator hears the' dis 60 least" .l5 R.M1S. equivalent Vof special signal to be re
ceivedÍ before contactsl AB and ABA will close.
tinctive'busy-signal of the call-receiver, »the initiator may,
Similarly, because of normal line and circuit attentua
atï'his discretion, still break through the call. shutout by
pushing his own button PB toV thereby enable his call to
tion, we have found it desirable to introduce into the line
operate.z the' bell- signaling circuit in, the call~receiverfs`
at’the sending end, by the special signal generator unit b,
65 approximately 2V v. R.M.S. equivalent value, although
lesser values will work satisfactorily if distances are not as
From a- functional standpoint, the operations outlinedY
great. “Cross-talk” effectv of this signal level is not objec
in FIGURE l may be implemented as follows: Switch
tionable because of the frequency employed and lesser'
Av--IBy could be a relay having several contacts which is
levels virtually eliminate any` such effect.
Vcontrolledb'y'an electronic timing circuit. The user could
Unit c, therefore, may consistV of a resonant tilter cir
thereby set the device in advanœ for a predetermined 70
cuit.' tuned',.forï example, to 2.8Í‘kc., followed by amplifier
period of timer in which minimumv interruption Vwas de
and relay operating circuits for closing'contacts AB4 and
sired; At the" end of that predetermined time, the tele~
ABA to re-esta‘olish the local bell circuit.
phonesi'gnaling circuit'would return to normal operation
Unit g may consist of an> electronic generator circuit,
even if the user forgot to restore the switching device
œt'o normal operation'.
75 and- amplifiers if- required, for introducing' an' alternating
current of the same frequency, 2.8 kc., to the telephone
line at an impedance of approximately 150 ohms, em
tery through R1 and contacts HJ, KL, MP, which thereby
ploying capacitative coupling.
Referring now to FIGURE 2, we have shown a modifi
timing interval. If the capacitor has not previously been
fully charged by the telephone line, as might occur if
the capacitor has very recently been discharged, the bat
assures a uniform capacitor voltage at the start of each
cation of my invention in which units f and g have been
combined, and unit f performs a double function. That is,
it generates the above described busy-signal and also when
button PB is depressed, generates. the special “remote-ring”
tery quickly charges it through relatively low resistance
actuating signal.
contacts MP, but no significant current ñows through TR1
because contacts MN connect its base to its emitter, mak
1 ing TR1 non-conducting. Therefore, there is no voltage
As an additional feature, we have found it practical to
transmit the distinctive busy-signal frequency of unit f
intermittently by switching it on and olf by a relay circuit
d operating at, say two or three times a second.
drop through R2, and so the base of TR2 remains biased
positive with respect to its emitter (the base current being
limited by its internal resistance and that of R4 plus R3),
distinctive interrupted tone helps to identify it as` a busy
signal since similar interrupting technique is standard
thereby making TR2 conducting. Relay RY1-is therefore
practice in most telephone installations for signifying a
line in use. Of course, in this instance, the frequency of
the tone is markedly different from the conventional busy
signal and indicates to those familiar with the system that
the called party does not wish to be intruded upon unless
essential. The use of interrupter relay d permits unit
e to be connected to the line only during those intervals
when unit f is disconnected thereby removing any effect
also actuated by the battery at the same time, through
R133, R8, coil RY1, TR2, R5 and contacts EF, MP. There
by, the relay
a. Disconnects the telephone bell circuit, contacts A, AN;
b. Connects the “green” (48 v. D.C.) line-wire to the
remainder of the apparatus, contacts B, BA;
c. Establishes a circuit to connect (when the starting lever
unit f might have on the performance of unit e, with a
consequent improvement in the reliability of operation.
The battery is also connected across the collector
and emitter of TR1 by a path through RE3, R8, R3, and
A further feature illustrated in FIGURE 2 is the pro
vision of a relay unit c which discontinues the busy-signal
is released) the positive capacitor terminal of C2 to the
moving arm of R1-contacts H, G; C; CA; the negative
capacitor terminal being permanently connected to the
base of TR1 through RE1; and
d. Holds the negative battery terminal connected to theV
from unit f during the time in which each regular ringing
“0.V. D._C.” line as long as the relay is closed (contacts
pulse is received, the busy signal being sent out only
between the regular ringing pulses thereby emphasizing 30 DA, D; which parallel contacts MP).
to the call-initiator that the phone of the party called can
When the starting lever 20 is released, contacts NM
still be signaled by the continuing ringing pulses if the
open, removing the “short-circuit” between the base and
calling party sends the necessary additional signal.
emitter of TR1, and contacts HG close, thereby placing
A circuit for the diagrammatic illustration of FIGURES
the anode of RE1 at 45 v. negative potential with respect
1 and 2 including an electronic circuit for controlling 35 to the moving armof R1 by means of a path through
switch A is shown in FÍGURE 3. In this ñgure, the
contacts C, CA. The resulting voltage drop across the units of FIGURES l and '2 are designated across the top
high back-resistance of non-conducting RE1 and the high .
and along the lower right hand side.
base-emitter resistance of non-conducting TR1 holds the
base negative with respect to the emitter, and therefore
Unit a. Tímer Controlled Switching Device
40 TR1 remains non-conducting and RY1 remains closed.
This circuit is entirely electronic, consisting of an elec
C2 is now shunted by R2 and R9 inseries, but effectively '
tric relay which performs the switching function. This
isolated from the remainder of the circuit by the very
relay is “closed” (actuated) at the start’of the timed
high back-resistance of silicon diode RE1 plus the rela
period, and “opened” at-the end of the timed period,
tively high base-emitter “back-resistance” of reverse-biased
and the timing is reliably performed, for intervals up to
non-conducting TR1 transistor. Thus, effectively, C2 dis
one hour and longer, by a unique transistorized “capacitor
charges through timer resistances R2 plus R9, and the latter
discharge” circuit which makes use of several unrelated
characteristics of standard manufactured components,
can be calibrated almost linearly in intervals of time. If
the arm of R1 were set at TR1 emitter potential, TR1
in pro-per combination, to provide unusually accurate time
would never become suñiciently conducting to develop
intervals and, at the end of the timed interval, relatively 50 a voltage drop through R3 which would shut off TR2 and y
sudden collapse of the otherwise constant relay holding
open relay RY1, since the base of TR1 must be made posi
current. In essence, the major purpose of the relay is
to disconnect the normal signaling bell circuit, contacts A,
AN, for the duration or" the timed interval, and simultane
ously to connect the line voltage, “green” +48 v. D.C. 55
tive with respect to'its emitter potential to cause TR1
conduction. Even then, because the tlow of a minute
base current through RE1 results in a voltage drop which
tends to bias the base negatively, the arm of R1 must be
wire, to the remainder of the device through contacts ì
B, BA, for use in units a through g as a power source
spect to TR1 emitter potential, to assure relay drop-out
and to provide the necessary path for the signaling func
anywhere from 3 to 4 volts positive, or more, with re
when the capacitor C2 is virtually discharged.
As capacitor C2 becomes nearly discharged and TR1
Capacitor C2 is normally connected continuously across 60 base potential rises toward and above emitter potential,
the 48 v. D.C. telephone line through resistor R6 and -
crystal-diode rectifier RE2 through contacts H, G; C, CN;
BN, B; and DN, D. This keeps the capacitor fully charged
and also as a result of the current amplification of TR1, the
last several seconds of capacitor C2 discharge result in
fairly rapid increasing voltage drop through R3. Because
and ready for use in the capacitor-discharge timing circuit,
of the amplification of TR2, and as its base potential drops
but more important, keeps the capacitor fully “formed” 65 to its emitter potential, the relay holding current is even
so that its internal resistance is extremely high. For
more suddenly cut-ott` to end the timing cycle. Thus,
example, itmay exceed 50 megohms when voltage has .
dropped from 48 to 40 volts, and is still higher at lower
even after intervals of one hour, the time required for
decay ofrelay holding current may be measured in sec
voltages. R6 prevents capacitor C2 from eñectively bridg
onds. Therefore, there is no danger of jarring the timing
ing the line to A.C. ringing currents, and RE2 eiîectively 70 relay open near the end of the time period, since the
disconnects the charged capacitor from the line when the _
telephone is in use and line voltage drops to relatively
holding current does not decrease as the capacitor voltage
decreases, and the timer circuit is substantially immune
to electrical and mechanical disturbances. It is virtually
When the timer starting lever 26 is depressed, capacitor
free from wear since the only moving parts are the start
C2 is instead temporarily connected 'acrossV the 45 volt bat 75 stop lever switch, the relay contacts and armature which
low values, such as 5-10 volts.
from short~circuiting these two' signals, since its inductive
reactance to their frequencies »is several thousand ohms.
L1 also serves this yfunction -for the other components in
act only at the start and the' end ofthe timed interval,
~ andthe time-set potentiometer whichneed not be moved
at all; until a different timeV interval is-~ desired.
units c, d e, f and'g which are connected to terminal RA,
Asa further reiinement, in step “b” referred to above,
the 48 v. D.C. line potential is connected through B,
Unit c.` Busy-S?gnalCutour during Ringing Pulse
BA toQ', (2N-to HB4, andv since REgis thereforeslig'ntly
The previously mentioned function of this optional unit
is to discontinue the special busy'signal during the interval'
positive with-respect to R133, the latter becomes noncon
ducting, and the telephone line supplies the approximately
Z'niilliampere'relay holding current-l, through RE.;` This ~ ' in which the incoming ringing pulse is lbeing received, on
small currentV drain causes line voltage to drop to about 10 the assumption that this may lbe of additional value in
emphasizingto the call~initiator that the ringing signal has
451/2416 volts. RE3 protects the battery from small re-
not been discontinued and, therefore, notwithstanding the
special Abusy-signal, the called party could still answer the
verse currentsv which would quicklyruin'it', and also assures
that even if the line voltagev drops further, throughiuse
of- the telephone or otherwise, thetimer will continue’
to function and the voltage variations across R1 will be
negligible. Battery drain inno'rrnal operation over any»
considerable period of time is therefore exceedingly small
call if hisfvbell‘were made to ring.
FIGURE 3 shows- switch SWZwhich may be used to
remove unit c from the circuit, should this be considered
desirable; with SW2 in the “on” position, unit c is fed line
voltage and incoming ringing signal by a path through
`contacts B, BA;’R, RA; and ACN, AC. Resistance R10
and battery life correspondingly greatly extendedl
Should it lbe desired to inactivate 4the timer before the>
isofl very high value, so it places negligible D.C. load on
the line, but it forms a voltage divider with the coil of the
preset time has elapsed,` thereby re-establishing the nor
mal telephone signaling function, itis only necessary to
D.C. relay RY3 which thereby prevents C5 from charging
move the lever switch 20 to the “stop”`position momen
to full line voltage. C5 is of relativelylarge capacity and
presents a relatively low impedanceto ringing sîgnalvolt
tarily, -for' this opens contacts EF breaking the relay coil
circuit, andthe relay drops outthusopening contacts B,
BA which had supplied relay holding current from the line 25 ages. Thus,-when a ringingpulse is received, the anode
of R137 spends most of eachA cycle at-a potential'which is
through contacts Q, QN. Contacts DA, D are also opened
positive withrespect to the O.V, D.C. line, and on in
and this disconnects the battery. so itwill not continue
creasing portions‘of the cycle, andas long as the anode
to.A supply current to any of the associated circuitry, for
of REq is’ positive with respect' to the positive terminal
this would also shorten its life.
Alternately, unit a'could consist of a conventional elec 30 of C6, it. charges C6 with sufficient current to hold D.C.
relayv RYgclosed'` for the duration of the ringing pulse.
tric clock motor. Since such devices are well known in
Therefore, contacts S, SN are opened during the ring
thel art and their function well understood, further eX
ingfpulse's and no current is supplied to unit d for inter
planation or illustration is not thought necessary.
Unil'b. Ringing SignatSensingy Y
mittently connecting thebusy-signal to the line. How~
35 ever, thisaction is initiatedv between ringing pulses at which
time RY3 is open andrcontactsS, SN are closed.
Y Capacitor C3 is intended to `couple AC. ringingsignals
tova'relay circuit which includes RYE, andÜto isolate this
Unit d
relayïcircuit from D.C. line potentialso no D.C. load will
“on” position actuating unitbe placedonthe line. When the timer relay RY', is closed,
capacitor C3 is charged'to line voltage (now about 46 v. 40 c, one set of contacts of SWZshort circuits R12. Between
ringing pulses 48' v. D.C. is applied through R13 to C8
D.C.) through contacts BA and L1 and~RE5~ When» an
which charges until.D.C.' Vrelay RYgcloses, disconnecting
incoming ringing pulse is received" (generally about 31?; v.
contacts U, UN'and removing the charging current. When
i A.C. superimposed upon about'46 v. D.C. fora duration
suiiicient- charge'on C8 has beenv dissipated, 'RY4 opens,
of about 2 seconds) the line voltage v_aries fromv about
and the cycleis ready to; repeat itself. A snap action is
ON'.' instantaneous potential to about>9tl'v., instantaneous
desirable and one way of providing this for all RY., con
(and vice versa) at ringing signal frequency.
tacts isas'follows.v
The> armature of RY.,v is held open by a small ñxed
magnet until more thannormal actuating current is flow
Assuming, at any given instant, »that the line voltage
is increasing to 90V., capacitor C3 isrïbeing charged to
nearly this potential, since RE5 is conducting, and the
resistance drop through L, is small and-its reactance- nearly
as> low at ringing frequency. As line’voltage decreases
from Y90 v;, the nominal 90 v; charge on C3 places its
negative terminal at a potential negative to the “D.V.
D.C.” line wire, and R135 ceasestoV conduct. Since the
ing. When the armature begins to rnove, it leaves. the
stronger area of magneticvñeld, allowing: the high actuat~
ingV current' to snap` the armature against the pole piece.
Whenthe armature opens, the magnet pulls it to a fully
open position, causing the contacts tomake a full-pressure
cathode ofv REG is thereby being made negative withre 55 low-resistance~ contact. This snap actionvof the electrical
>contacts preventsthearmature from idling at a midway
spect tothe O.‘V. D.CL line, to which its anode is con-V
position where contacts U, UN are touching with a high
nected by the low impedance of C4, RE begins to conduct
resistance contact which reduces the coil current and stops
, and to charge C4 from the' charge contained in C3. This»
C4 charge accumulates to about 50 volts in 2 seconds'. ' the armatureV fromV movingY further. When RY, is ac
Relay RY2 closes at' l2 volts, or about. l/á second after 60 tuated, contacts U, UA shunt CS with a resistor, R14, that] '
acts to decrease the discharge time required to open RY.,t
the‘tirst ringing pulse begins, and the large capacity of
which would> otherwise stay closed much longer than it
C4' holds this relay closed for about 5 `seconds until the
'was open. By adjusting Rlsvand C8, for the time the relay
next pulse is received. Thus, relay RY2 closes virtuallyv
remains open, and R14 for the timeit remains closed, the
at the start of the tirst pulse of the ringing signal and
stays closed until the ringing signalV has ceased (the latter 65. intermittent action of RY4 may bef‘shaped” toa uniform
openjclosed sequence at a rate of about 2 cycles per sec
being caused by either theï call-initiator “hanging-up” to
ond. When RY.;V is closed, contacts T, TA connect the Y
discontinue his call, or by the call-receiver lifting his
busy-signal (generated by unit f) to the telephone line
handset from the‘cradle which bridges the line and ac
through QA, Q and BA, Bg'whenA RY4- is open, contacts
tuates the'ring-cut out> relay at‘the central odice), thereby
assuring for the identical duration ottime that contacts 70 T, TN connect the line to the input of unit e so that any
incoming “remote-ring” signal may be utilized. This re
Q, QA and R, RA remain closed to carry out the other
ciprocating action prevents any busy-signal output'from
functionsof the device. Contacts Q, QA Vfeed all line
enteringunite input> and possibly >adversely aiîectingY this
voltages and any desired incoming special “remote-ring”l
signal. to unit e, and feed any outgoing busy-signal to the
telephone line; inductance L1 prevents> capacitance C3
circuit’s operation.
The above relayaction also takes place when SW2 is
3,033, 941
thrown to the “off” position, with the exception that this
action continues during the time a ringing pulse is being
the decay of the busy-signal generated by units f, g which
would otherwise remain for several seconds.
The busy-signal has now stopped, and the caller hears
received, the call-initiator hearing the ringing pulses with
intermittent busy-signal superimposed. Also, when SW2
only the ringing signal, indicating that the bell (or other
is “ofi” R12 is added to unit d, as is C7. This is to vir
signaling device) of the called telephone is now being
signaled. At this time RY5 is held closed by line voltage
fed through R27 and contacts R, RA of RY2, and there
tually eliminate the eifects of A.C. ringing signal upon
the timing interval of RY2 operation. C7, of large capa
city, charges through R12 and maintains a relatively con
fore the signaling (bell) circuit will remain re-established ,
by AB, ABA as long as RY2 is actuated, i.e., as long as
stant voltage as a source of power to R13, C9 and RY1
even when individual cycles of ringing pulses swing the 10 the ringing signal continues, and for about 5 seconds
“SN end” of R12 above and below average C7 potential
after the last pulse, when the charge on C4 has virtually
at its positive terminal. Since the average value of the
been dissipated permitting RY2 to open. Thus, when
ringing signal voltage is about 46 volts, this also tends
either the caller discontinues his call, or the called party
to keep C7 charged to this value during ringing pulses,
“answers” his telephone, RY2 opens, RY5 follows, and
less the drain caused by the relay circuit. Obviously, if
the device returns to starting condition, ready to repeat
it is decided that SW2 could be left permanently in either
the above sequence upon receipt of a subsequent ringing
position, this switch could be omitted along with the
signal followed by the “remote-ring signal” if one should
components which would not be utilized. Long term
be sent by the call-initiator. Where no special signal is
eäectiveness of operation balanced against cost of com
received, RY5 does not close, the bell does not ring, the
ponents would help decide this question.
busy-signal continues until the caller discontinues his call;
when the ringing signal ceases, RY2 opens, and power is
Unit e. "Remote-Ring Signal” Sensing
removed from contact RA and units c, d, e, f and g of
Contacts T, TN feed, to unit e input capacitor C9,
the D.C. line voltage, ringing signal, switching transients 25
(at start and end of ringing pulses), random line noise,
and, if being received, the 2.8 kc. remote-ring signal. C9
is a D.C. isolation capacitor, as is C11, and they present
a medium impedance path to the 2.8 kc. signal, and a
proportionately higher impedance to lower frequencies,
particularly regular ringing frequencies. L2, C10 com
the device.
Units f, g. Busy Signal Generator and Remote Ring
Signal Generator
When RY2 closes upon receiving the first pulse of an `, incoming ringingsignal, line voltage is applied through R, '
RA; ACN, AC; and R24,_through which the current drawn
30 by units e, f and g causes the voltage to drop to 24 v. ‘
prise a parallel resonant circuit tuned to 2.8 kc., having
reasonable Q, and thereby peaking signals at this fre
D.C., and this voltage is applied to decoupling capacitorC18 Whose large capacity maintains a relatively stable
D.C. voltage even when “A_C. plus D_C.” ringing pulses '
are introduced to the input of R24. This “stabilized” '
mon-emitter transistor ampliñer stage with a voltage gain 35 D_C. voltage is then applied through contacts WN, W to .
of about i60 at 2.8 kc. Emitter by-pass capacitor C12
to the generator unit f, g-with the return circuit through ‘
is purposefully small, to permit current feedback in this
TR9 and associated circuitry comprise a com
stage by means of emitter resistor R12, thereby consider
TR7 oscillates in what could be called a Colpitts type
ably reducing gain at lower frequencies. Capacitor C12
circuit, C22 and C23 being proportioned to supply the feed~
bypasses higher frequencies between base and emitter. 40 back, and their series capacitance tuning L9. The output ‘
Therefore, the frequency response at .the output-capacitor
C13, shows a very sharp peak at 2.8 kc., with voltage re
sponse at 2 kc. and 4 kc. being»“down” about 100 times
as compared with a 2.8 kc. signal fed into C9. The out
put from C13 is fed to a common-collector transistor stage
to provide low impedance output for charging capacitor 45
C16 with half-waves of 2.8 kc. signal which have been rec
tiiied by RE9. Capacitor C16 is coupled to the low im
pedance base-emitter input of power transistor TR5 which
is fed through C21 to transistor amplifier stage TR6, and '
the outputV of this stage through C29 to the impedance- ‘
matching output transformer, T1, which is coupled to
the line through C19. This coupling proceeds through
TA, T; QA, Q; and BA, B when the intermittent busy~
signal is being generated, the interrupting being per
formed by contacts TA, T. The signal level on the line '
is about 2 v. R.M.S. equivalent, at a frequency of about
>900 C.P.S.
was selected for its low collector-emitter resistance when
The “remote-ring” signal is normally generated only '
conducting. Suñìcient charge on C16 causes TR5 to con 50 when the telephone is being used to place a call to an
duct, thereby actuating relay RY5. A 2.18 kc. signal of
other user whose telephone is similarly equipped and
about .l5 v. RMS. equivalent value introduced to C9
who has temporarily disconnected his signaling (bell)
. will cause the relay to close. Much additional sensitivity
circuit which is indicated by a busy-signal generated at
his telephone. Since the caller’s telephone is now in use,
the line voltage has dropped to approximately 5-10 volts;
Therefore, the “remote-ring” push button 30 may also be
could be obtained by increasing the values of C9 and C11
retuning C10 as required-and by reducing R21. How
ever, this is not recommended as switching transients and
random line noise may actuate RY5. R26 presents a
used to connect the 45 v. battery to unit f, g -to supply
slight bias to TR5 input in order to maintain cut-ofi even
power, through R11, WA, W and YA, Y. R11 may be
with small charges on C15 accumulated through rectiiica
adjusted for desired 2.8 kc. output signal level. Note
tion of the above mentioned extraneous random voltages. 60 that XA, X by-passes the contacts TA, T and QA, Q on
C17 prevents RY5 from closing as a result of any short
relays RY4 and RY2, inasmuch as these relays have not
duration transients charging C16 to a level which might
been actuated. Also, note that L2, of relatively low in
cause TR1, to conduct instantaneously.
C12 acts as a
ductance, has been paralleled with L3 through VA, V.
Thus, L2, having lower impedance, determines the fre
“sink” to maintain relatively steady D.C. voltage at the
arm of R21 in spite of the A.C. ringing pulse excursions. 65 quency of operation which is now` higher, and this is
tuned to 2.8 kc. by adjusting the series sum of C22 and
When the presence of a 2.8 kc. signal causes RY5 to
C29, keeping their individual values proportioned for best
begin to close, contact ADA connects with AD in a “make
feedback. R31 and R32 can be proportioned to make the
before-break” sequence which applies about 22' volts,
reduced from line voltage by R27, to the relay coil, as 70 oscillator frequency virtually independent of supply volt
age over a considerable voltage range, although the col
suring its complete closure. This closes contacts A8,.
lector-emitter voltage rating of TR7 must not be ex~
ABA which re-establish the telephone signaling (bell)
ceeded. This will assure reliable “remote-ring” operation
circuit, and opens contacts AC, ACN which remove power
over the life of the battery.
from units c, d, e, f and g, discontinuing their operation.
‘Output capacitor C19 serves several functions. It does
Contacts AC, ACA help to discharge C12 and so hasten 75 not pass D_C., and therefore does not permit the output
l l»
Winding of T1 to bridge the line and operate the ring-cut
oli- relay at the central oñìce. So, neither does this wind
ing cause reduction of thev line voltage which is being used
necting a primary signaling circuit of_ a. telephone for a
predetermined period. of‘time, said‘ predetermined period
as' a_D.C`. power source. The relativelyy low value of C19k
oifersk a.- reactance of several thousandl ohms to vringing
currents, and” therefore has negligible eiîect in this re
capacitor discharging .through` a resistance which con-k
trols the switching. of the contact of the electric timer,
means for generating and transmitting to a second calling
station upon receipt of ringing voltage a distinctive busy
being controlled by'anelectric timer, said timer having a
spect; Yet, it or’i‘ers suiñciently low impedance to, the.
busy-signal yand -a lower impedance tothe “remote-ring”
signal' indicating the disabled condition of the primary
signaling circuit at the iìrst station', means for maintaining
signal generatedA in unit f, g-Coupling both to the line,
10 îhering-cut-oiî relay at the central station unactuated
during generation of the distinctive busy signal, means
The total D.’C. load on Vthe line„for operating all theV
relays andî the` transistorcircuitswhichmay be in use
for generating an additional signal at the second calling
4station, operable' to disconnect the disablement of the
at any one time, is so low. that the central-office` ring
cut-oilV relay is not actuated,` permitting latert use ofthe .
continuing ringing signal*V for ringingthe local signaling
i l
primary signaling circuit, and means for re-establishing the
15 previously disabled telephone signaling circuit upon re
ceipt of the additional> signal.
While we have shown and described an embodiment
7. In ay communication system,V means for disabling a
ofour invention, it Will be understood that the diagram
matic and schematic illustrations and description of opera-V
»tion are intended to be illustrative only .andl the scope of
o the invention should be limited> only by the scope of the
primary signaling circuit in a telephone at a first station
hereinafter appended claims.
- We claim:
for a predetermined period of time, said meansincluding
an electric timer operating on very small quantities of
` power drawn from the main telephone line whereby nor
mal telephone operation is unañected, means for gen
erating and transmitting .to a caller at a second station,
upon receipt- of ringing voltage, a distinctive busy-signal
l. In combination in a telephone system having aV
ring-cut-oiî- relayy at a central location, means for tempo 25 indicating tl'iel disabled condition atthe tìrst station, means
for generating; an additional signal at, the second station
rariiy disabling a primary signaling-circuit associated with
for counteracting the disabledi condition ofthe primary
signaling circuit, and means-tor4 rte-establishing Vthe previ
ouslyA disabled telephonev signaling circuit upon receipt of
a receiversuch as a telephone atA a iirst station without
actuating the ring-cut-off relay, means- for' generating a
distinctive busy-signal. at the first station ‘uponreceiptofï
conventional ringingvoltlage, means for transmitting the
theadditional signal.
8. In a, communication system a> primary telephone
distinctivei busy-signal ; to a . second Y station, and means . for
signaling circuit interrupting means adapted to selectively
.re-establishingy the temporarily disabled primary signal
ingv circuitî after receipt of> the distinctiver busy-signal Vin
» disable- they circuit» for predetermined periodsof time,
an electric timer for maintaining the disabled condition
cluding generating means for producing anv additional
signal aty the second station and meansv for transmitting 35 ofthe primary signaling circuit,Y said timer beingfoperated
by very small quantities of power derived fromthc main
theradditional signal to the first station.for’couuteracting
the temporary Vdisablement of the >primary signaling " telephone line whereby normal, telephone operation is v
unaffected, means. for generating and. transmitting to a
second station, upon receipt of ringing voltage at the
¿2... In'- aY telephone system having a ring-cut-oif relayv atr
a central. station, means for selectively disabling a pri 40 first station, a distinctive Vbusy-signal 4indicating the dis
abled condition> at the iirst station, means for preventing
mary> Signaling circuitV iny a telephone at` »a first@ station,
means for generatingand transmitting to a. caller at a
actuation. of at ring-cut-otî relay lat the central office,
' second station, upon. receipt of ringing voltage «at the
first station, a distinctive busy-signal indicating the selec-V
means for generating Vadditional._Signal at the second sta
the ring-'cut-otîv relay at the central'station from operat
tion capableof counteracting the disablement of the pri
mary signaling circuit, and means for ice-establishing the
selectively- disabled primary signalingr circuit in response
ing, means for producing atV the second stationV anaddi- l
to the additional signal.
,tional signal for counteracting the selective disablement
of the primary signaling circuit and means for Vre-estab
9.111 a telephone system having a ring-cut-olî relay at
a central station, a-call' receiving station, said call receiv
ing station including a telephone receiver having a signal
ing circuit, and' a callv initiating station; ymeans for dis
connecting the signaling circuit at the call receiving sta
tion, means for generating a distinctive signal in response
to an incoming ringing signal without Iactuating the ring
' tively disabled condition, holding means for preventing
lishing the selectively disabled primary signaling circuit`
upon receipt ofthe additional' signal;
3. In a .communication system, means for'disabling a
primary signaling circuit' in al receiver at a first station,
said disabling: means including an electricy timer device
for- controlling a switching» element inl an electric timer, -
l"said switching element being effective to disconnect the
cut-oä relay tothereby indicate the disconnected condi
tion of the signaling circuit, means for transmitting the
primary signaling'circuit from main line'voltage, means
distinctive signal to the callV initiating station, and means
for generating and sending to a second station upon re
for edectively tie-establishing the disconnected signaling
ceipt of'ringing voltage at the Íirststation aV distinctive
busy-signal indicating the disabledícondition,A means for
generating and sending an additional' signal to the first .
station for counteracting-thedisablement‘of the» primary
signaling circuit, and means for re-establishing the previ
ously disabled telephoneY signaling> circuit responsive to ,o
the additional signal.
4. The system-of claim’3 wherein the primary signaling Y
circuit is a bellV circuit.
5`. The communication system of- claim 4' wherein the Y
electric timer device is aV capacitor discharging through a
6. In a communication system having a ring-cut-off re
lay at a central station, means for ‘temporarily discon-YV
circuit at the call receiving station, said re-establishing
means including means for generating a signaling circuit
restoring signal at the call initiating station and trans
mitting it to thecall receiving'fstation, and means at the
call receiving station responsive to the restoring signal
which eñectively restores the signaling circuit.
References Cited in the tile of this patent
Hardgrave _______ __'___ Sept. 13, i949
Lutz _, ________________ __ Aug. 9, 1955
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