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Патент USA US3033939

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United States Patent Ollice
.lames T. Neiswinter, Garden City, NY., assigner, by
Patented May s, 1962
point of +15, to a swing of +43 to +39 at the base of
T3 which has a mid-point of +2. This centers the swing
around approximately +2 volts lon the emitter of T3 and
mesne assignments, to The Pioneer Electric 8; Re
results in no bias to transmission -from the send hub
search Corporation, Forest Park, Ill., a corporation
through T3.
of Illinois
With the send hub at +60 corresponding to a mark
Filed Nov. 10, 1959, Ser. No. 852,106
signal voltage, and the voltage on the base of T3 at +43,
T3 will be non-conducting. Under this condition, the
current Ithrough the windings of «the send relay will be
The present invention relates to an improved telegraph l0 approximately seven mils, as determined by +130 volts
repeater unit and more particularly to a transistor-ized cir
through R18 to the windings. Since the resistance of
cuit which is a direct plug-in replacement for existing
the windings of the relay is only 272 ohms, the parallel
coupling units in commercial systems of the general type
branch of 5.6 K ohms to ground will have little eiîect on
disclosed, for example, in U.S. Patent Nos. 2,607,852 to
the winding current. The seven mills current will be in
Rea and 2,636,942 to Davey. In commercial practice
»a marking direction to hold the armature of the relay
certain operating conditions and voltages have been stand
on mark.
9 Claims. (Cl. l78-‘73)
ardized and are well known to those skilled in lthis art,
and the following description will assume an understand
.The voltage at the collector of T3 is limited to -24
volts by diode D4. Current will be flowing through R14
ing of this art.
and D4 while T3 is non-conducting. The purpose of
A principal object of the present invention is to pro 20 diode D4 is to limit the voltage at the collector of tran
vide an improved inexpensive, easy to service, direct
sistor T3 to a value within the yrating of the transistor.
plug-in replacement for prior leg coupling units common
Resistor R19 is only for the purpose of protecting the
ly referred to as a 144A1 circuit. While the present in
transistor at a time when a -24 volt fuse might blow. In
vention has essentially the same electrical characteristics
this case, with the -24 volts absent, the path to ground
viewed externally, because of being a transistorized cir 25 through ‘R19 will limit the vol-tage at the collector of
cuit adapted to use three transistors of the `same type, con
siderable variation of internal circuitry has been found
necessary to provide a practical unit which will comply
with the strict testing and exacting standards 4reqin'red
in this industry,
Referring now 4to the drawing wherein the circuit dia
gram of my improved coupling unit is illustrated, the uni-t
comprises a receive leg having the usual receive relay
with -alternate contacts connected to positive and negative
voltages and connected to the receive hub. The send hub
is conventionally connected, either directly or through a
regenerative repeater 10 by contacts l2 and 14, to the
receive hub. The send leg is connected vfrom the send
transistor T3 -to -about -26 volts.
yIn the idle and in the marking condition of this circuit,
all three transistors are non~con2d-ucting~
When the receive hub `goes spacing due to a space being
received on another repeater connected to the hub, the
lsend hub goes spacing, its voltage becomes _30, and the
voltage applied to the base of T3 becomes +39. This
causes transistor T3 to conduct and a current of approxi
mately 14 milliamps to flow through R14, through tran
sistor T3 and the relay windings in a spacing direction to
ground. This 14 rnilliamp lspacing current overrides ,the
7 nulli-amp marking current Ifrom +130 volts through
R1=8 and causes a resultant current of 7 milliamp 'spacing
hub. Varying numbers of from 2 to l0 or more lines
which operates the relay to spacing. Thus, any space sig~
are connected to the receive and send hubs, each having 40 nal occurring on the send hub due to a space being re
a plug-in unit such as ‘that illustrated in the drawing.
ceived from any other repeater on the hub is transmitted
With the receive (R) leg of the repeater to which the
unit is connected in the mark condition, and the receive
and send hubs also in the mark condition, »the voltages
at the various points inthe circuit Iare as indicated for con
dition “MM.” In these designations, the iirst letter'indi
cates the condition of the R leg of the repeater associated
with the unit, and the second letter indicates the condition
of the R leg of another repeater >connected through a
to the send relay directly with no holding action taking
place, since transistor T2 is non-conducting under this
The operation of the receive relay to space of the re
peater connected to the R leg of the control circuit (Con
dition SM) causesl the voltage on the receive hub to
change of +60 to _30. At the same time the voltage
on the send hub will change to -30 immediately if there
coupling unit to the same receive hub. In the MM lcondi 50 is no regenerative repeater between the receive and send
tion, transistor T1 has +22 volts on its base and +8
hubs, or in about halfvavjunit pulse length later if there
volts on its emitter and is therefore normally non-con
is a regenerative repeater between fthe two hubs. The
ducting since no current liows from base to emitter when
function of `the control circuit in this case'is to prevent
the base is positive with respect to the emitter.
.the space voltage on the send hub from operating the
Considering transistor T2, the voltage applied to the
send relay to spacing and thus sending a space back to
base of this transistor results from »the +130 volts through
the originator of the space pulse on the receive siderof
R4 and R5. This voltage, as applied to the one terminal
the circuit.
of capacitor C1, is limited to +8 volts .by the diode
' When the receive relay -in the lreceive leg of the illus
across the collector and emitter of T1. The +8 volts
trated circuit goes to spacing, 'the voltage at `the top of
on the ungrounded terminal of capacitor C1 is applied 00 R4 changes from +130 to about _120 volts, which
directly to the base of T2 through diode D3 which shunts
causes a voltage ofabout _22 volts at the junction of R4
resistor R9 for this polarity. TZ is therefore normally
and R5. This -22 volts will be applied directly through
Inon-cornîlucting, and under this condition will have no
diode D2 to capacitor C1 and will change the voltage on
effect on the operation of_ T3.
rthis capacitor from its MM voltage 'of about +8 to -22
Considering transistor T3, with the sen-d hub in the
volts for the SM condition. The change in voltage on
MM condition, a voltage of +60 is conventionally avail
capacitor C1 will take a few nulli-seconds to complete.
able ony the send hub and is applied through Rî6 to the
However, when the voltage has changed only from +8
base of T3. rllhis voltage is reduced by the -130 volts
to +4, transistor T2 will conduct.> The change of voltage
applied to the base of T3 through R15. The circuit
of this amount takes less than one milli~second.
through R15 is for the purpose of changing the +60 to 70 When transistor T2 goes conducting, ythe +5 volts on
‘_30 (the conventional space signal voltage on the send
its emitter is applied directly through the emitter-col
hub) voltage swing on the `send hub, which has a mid
lector path of the transistor and through diode D5 to the
. 3,033,929
on the occurrence of a double space on the receive hub
through 180,000 ohms, the +5 volts will hold the base of
sistor T3 from conducting.
'Considering the circuit-to the baise of ¿transistor TV1, 4
' when the voltage of the receive hub was: +60, the voltage
A'on the base of T1> was +22, and accordingly transistor
T1 was‘non-conducting. When the voltage on the _re
ceive-hub goes to -30 for the SMor the MS condition,
the voltage at the 'base .of transistor T1 goes to:.+l7
which still leaves transistorV T1 non-conducting.' There.
fore, during the SM condition lbeing described, transistorV
T1 will remain non-conducting throughout and need not
be considered in the holding action .on transistor T3
lunder discussion. >Transistor T1 conducts only under `the
SS condition.
When the receive relay returns to the marking condi
tion it is necessary that the holding etlîect of transistor T2
on transistor T3 remain for nearly the length of a unit
pulse. This is ,to provide for the case where regenerative
repeater 10 is used betweenthe receive and send hubs,
due to two receive legs going spacing atV the same time,
the holding action on transistor T3 of the coupling unit
is removed andthe space is transmitted through the unit
to the associated send line. Since whenv the double space
occurs and ltransistor T1 goes conducting, the discharge
>of C1 and the change of transistor T2 from conducting
to noni-conducting occurs in less Vthan one rnilli-second,
thereis practically no delay in the vtransmission of the
double space through the unit.
»The presence of R17 being connected to the send hub
,is important as it performs two distinct functions. One is
»that 'it presents an artificial load to the send hub during
Vthe marking condition. Its value is selected so that this
load matches the load presented to the send hub during
»the spacing condition by the circuit to the base of tran
20 sistor T3. The two loads are not equal in micro-amperes
but are of such value that the voltage drop on the send
hub is the same for both the mark and space condition.
Thus, the addition of a considerable number of legs to
the send hub will not cause bias since, with the mar-k and
space loads on the send hub balanced for each coupling
in which case the space on »the output of the regenerativeV
unit, it is comparable to a polar circuit in which decreas
repeater will be lagging sometimes nearly a pulse length
ing the resistance of the circuit, and correspondingly in
behind ,the space on the input when the receive leg signals ’
creasing the current ñow in the circuit does not cause
bias because the increase is balanced for the mark and
have a large marking bias. It the hold on transistor T3
removed too soon, the last part of this space pulse will
-be transmitted to the send line.
The `delay in the removal of the hold on the base of
transistor T3 is obtained from the circuitry involving
space conditions.
-conducting. When the receive relay goes to marking,
»the positive +130 voltsV that appears at «theriunction of
R4 and R5 is blocked by diode D2 and must be` applied
to the capacitor through R13 which _has a high value.
Transistor T2 Will therefore remain conducting until the
voltage on C1 changesfrom _.22 to about +5. The
coupling units might be separated from the send hub.
This will cause transistor T3 to conduct and send a deñnite
35 space signal to the send line during such a condition,
thereby giving a warning to the distant oiiìce that it is
cut off the hub. If the send leg did not go open deñnitely
under this condition, the distant end might remain _in
a closed condition and cut oft' lfrom the hub .for a con
siderable time before becoming aware it was no longer
on the circuit.
values of C1 and of R4 and R5 are selected so that this
Thus, the complete holding action'is that when the
lreceive relay goes spacing, the voltage on C1 ,changes
quickly from a value of about +8 to the +4 value
Without the added current from R17,
VVthe amount of base-emitter current in transistor T3 might
delay .is approximately one pulse length at sixty speed
transmission or 22 nulli-seconds. It is, therefore, ample for
H60 w,p.m., and also fior higher speeds which recìuire less
Another function of Ri7 is Vto create more base
emitter current in transistor T3' during a time when the
capacitor C71. During the SM condition the` voltage on
the _capacitor was about Y--22 volts and transistor T2 was
-to spacing to ysend a space onvthe send line .of this re
peater. This is called a double-space by-pass action, since ‘
T3 positive even though the send hub is- at +30 volts,'and
a conducting condition in transistor'TZ Will’preveut tran-V _
will thereforego conducting and operate the send relay
base of transistor T3. Since this +S volts is applied
through only 680 ohms in the »emitter circuit of transistor
T2 and since the _30 volts from the send hub is applied
be insuiiicient to drive the transistor completely con
ducting. The value of R17 is preferably in excess of 5
45 megohms with the voltages indicated in the drawing.
Diode D3 is connected around R9 so that when the
voltage on capacitor C1 is positive ¿this voltage will he
applied to the base of transistor 'T2 through a low re
sistance instead of through the resistance of R9 which is
»necessary to make transistor T2 conduct, and then con
high. This improves the perfor-mance of the transistor
tinues on to a value of -22 volts for the steady state 50 considerably
at high temperatures since the leakage cur
spacing condition. Then when the receive relay returns
rent that iìows from collector »to base in the transistor
to marking, the voltage` on the capacitor slowly changes
during high temperature conditions can not, in its tiow
VLfrom -22 volts back to +8, holding transistor T2 con-Y
diodes D3 and D6 and resistors R11 and R10,
ducting long enough to allow a space pulse being trans
cause' sufficient voltage drop to change the voltage `at the
mitted on the send ,leg by a regenerative repeater to vcorn
`pletebefore vtransistor T2 is made non~condueting and
base of transistor T'Zrfrom a positive to a negative value.
Without the diode around R9, the leakage current would
the hold onthe base of transistor T3 is removed.
create such a voltage drop through this resistor lthat the
,'If, while a space is being received on the receive relay
voltage at the base of transistor T2 would become neg
and While Clis charged to -22 volts and transistor T2 » ' ative at `fairly low temperatures. When the voltage at
is conducting to’hold transistor T3 non-conducting, an 60 the base o-f »transistor T2 becomes negative with respect
other repeater associated with the receive hub sends a
to the emitter, the transistor will conduct. This would
space to the hub (Condition SS)` the voltage on the hub
cause a holding action on the base of transistor T3 even
will change from --'-30 to -60 volts. This is the so-called
'double-space condition of the hub.
at times when Vtransistor T2 is intended Ato be non-con
ducting.' Signals would therefore be blocked on the
Y When the receive hub voltage becomes _60, the voltage 65
send leg during times when they were supposed to be
applied to the base of transistor Ti becomes -5 and
transistor T1 will conduct. During the conducting con
dition, of course, the voltage measured at the base of
transistor'Tl will be the `same as the emitter voltage
4 which is +8 volts.Y
When transistor T1` conducts, it discharges C1 in less
than a milli-second and causes the voltage on C1 to be
come +8. With the voltage >on C1 equal to +8, tran- Y
' Inhalt duplex` operation, assuming no regenerative re
i peater, and a'low capacity hub, the conduction of tran
sistor T2 when the receive relay goes spacing must occur
before the voltage on the receive and send hubs in com
Vbination changes from +60 to +15, which is’the point
at which thesend relay goes spacing. This is accom
plished by making the charging action on C1 fast so that
' sistor T2 willV go non-conducting and remove the holding
voltage from the 'base of transistor T3. Transistor T3 75 it reaches a voltage sutiicient to make transistor T2 con
duct very quickly. In the case of a very low capacity
hub (only one or two legs connected), the voltage on
the hub changes to the spacing value quickly enough to
p make a slight change in the mark current through the
send relay before the hold through transistor T2 is ap
plied. This change of current is so slight that the arma
ture of the relay does not operate at all and no harm is
caused by the slight current kick that occurs. Under the
condition of more legs on a hub, the change of voltage on
the hub from mark to space will be slower and no cur
rent kick on the send relay winding current will be ob
served. When a regenerative repeater is used, the ap
pearance of the space voltage on the send hub, of course,
is delayed usually many milli-seconds and no kick at all
will be observed in the send relay winding current.>
In the case of full duplex operation, where the voltage
on the receive hub changes from _10 volts for mark to
-60 volts for space, it is necessary that before the volt
age on C1 can change sufficient to cause transistor T2
to conduct and place a hold on transistor T3, that tran
sistor T1 be driven conducting to clamp C1 collector at
the voltage of +8 which will hold transistor T2' non
conducting. This quick action of transistor T1 on full
duplex operation is obtained through resistors R6, R7
appended claims rather than by the foregoing descrip
tion, and all changes which come within the meaning
and range of equivalency of the claims are therefore in
tended to be embraced therein.
What is claimed and described to be secured by United
States Letters Patent is:
`1. A hub telegraph repeater unit of the type adapted
to be connected to a receiving hub and a sending hub,
said repeater unit comprising: a receiving leg having a
receiving relay connected to said receiving hub through
an impedance, a sending leg having a sending relay con
nected to said sending hub through an impedance and a
tirst transistor normally non-conducting to causerthe send
ing relay to be in a marking condition; a iirst control
stage having a second transistor normally non-conducting
when the receiving leg is at rest; circuit means for con
necting said second transistor to said first transistor for
preventing said iirst transistor from conducting even
though a space signal condition is present on said sending
hub; means including a resistance, diode and capacitor
connected to said receiving leg between said receiving
relay and Vsaid impedance for selectively charging said
capacitor when said receiving leg has a space signal there
on; means for connecting one terminal of said capacitor
and R8 and capacitor C2. It should be observed that the 25 to said second transistor to cause said second transistor
voltage at the junction of R7 and R8' is about -22 volts
when the receive hub is at any value more positive than
this, due to the blocking action of diode D7. When a
space does occur on the receive hub, and the voltage
to control said ñrst transistor and prevent the sending leg
from transmitting a space signal; and a second control
stage comprising a third transistor; circuit means for
connecting said third transistor to said receivingrhub and
changes from -10 towards -60, it will change only from 30 to said one terminal of said capacitor for preventing said
-10 to -22 before the effect of the voltage change is
capacitor from becoming charged when a space signal
transmitted through C2 to the base of transistor T1.
condition is simultaneously supplied to said receiving hub
Therefore, for only a l2 volt change in the voltage on
from a plurality of receiving legs.
the receive hub, transistor T1 will become conducting and
2. In a hub telegraph repeater unit adapted to be con
clamp capacitor C1 at +8 volts. This action will occur
nected to a receiving hub and a sending hub, said unit
before the voltage change on capacitor C1 due to the cir
having a control circuit interconnecting receiving and
cuit through Rd has had time to bring the voltage on
sending legs for a single circuit for locking and unlock
capacitor C1 to the value required to make transistor T2
ing said sending leg in response to signaling conditions
conduct. Therefore, on full duplex operation where
impressed on said receiving leg comprising a first tran
signals on the send side of the circuit must not be inter 40
sistor having base, collector and emitter elements, a first
fered with by signals on the receive side, any space pulse
circuit means connecting the base element of said first
transistor to said sending hub, means for connecting the
emitting element of said first transistor to send relay
cause no hits to transmission on the send side. ln the
sending leg and through a >ñrst ini
case of added capacity to the receive hub, the change 45 pedance toin asaid
source of positive potential whereby the
of the voltage from _l0 to -60 on a space will occur
current conduction of said first transistor controls the .
more slowly. If it occurred slowly enough, transistor T1
of the sending leg, means connecting said col
would be slow in becoming conducting and transistor T2
lector element to a first source of relatively small nega
would conduct momentarily before transistor T1 became
conducting, and, during a time when a space was being 50 tive voltage through a diode and to a second source of
larger negative voltage through a second impedance, and
transmitted on the send side, a mark-to-space transition
a third impedance connected from a common connection
on the receive side would cause a marking hit on the
between said small negative voltage source and said diode
send side. The circuit of the present invention will oper
to ground, said diode being so poled as to protect the
ate at full duplex with a capacity of over .5 MF on the
receive hub, which is considerably more capacity than 55 transistor from excessive collector voltages. .
3. The repeater unit as defined in claim 2 further hav
would exist in practice on full duplex operation.
a fourth impedance connected between said emitter
On half duplex operation, the network to the base of
element and ground to prevent excessive voltage on the
Tl causes no load on the receive hub for the MM condi
emitter element when the send relayv windings are re
tion, and only causes a load when the voltage on the
moved from said repeater.’
on the receive side will make transistor T1 conduct before
transistor T2 can conduct and therefore transistor T2 can
hub reaches -22 volts or more. This voltage is consider 60
ably beyond the changeover voltage of +15 at which
the send hub is to go from mark to space. Therefore,`
the operation of the send relay will have occurred before
the network produces any load on the hub and ktherefore
the network will cause no bias to signals even when l5
to 20 coupling units are connected to the same hub.
Resistors Ri and R2 comprise the circuitry for the
hit locator of a No. 2 service board.
These resistors
are the same as are used in the prior l44A1 unit and the
4. The repeater unit as defined in claim 3 further hav
ing in said ñrst circuit means an impedance having a
resistance of at least 5 megohoms connected to a nega
tive voltage source of 130 volts to match the load pre
sented to the send hub and to create added base-emitter
current in said transistor so that if said transistor should
become disconnected from said send hub, a space condi
tion will -be sent to the distant oflice connected to said
send leg thereby warning it has been cut-off from said
sending hub.
theory of operation is the same.
The invention may be embodied in other specific forms
nected to a receiving hub and a sending hub, said unit
Without departing from the spirit or essential character
having a control circuit interconnecting receiving and
istics thereof. The present embodiment is therefore to
sending legs for a single circuit for locking and unlock
ing said sending legs in response to signaling conditions
strictive, the scope of the invention being indicated by the 75 impressed on said receiving leg comprising: a ñrst tran
be considered in all respects as illustrative and not re
siStOr; `a _first circuit means including a large impedance
' . v7. The repeater nnit as defined in claim 6 wherein »said
connecting a .control element `of said fñrst Y'transistor to '
second `circuit means is connected to the receiving leg at
saidrsending hub; means for connecting another element
a point between thereeeivev relay and the receive hub.
8. The repeater unit asïdeiined in clairn 5 further hav
ing a third transistor having collector, base and emitter
of said tirst transistor to said sending leg whereby the
current Vconduction of said iìrst transistor controls the
operation of the sending leg; a second transistor having
emitter, >collector' and base elements with the coliector
element connected to control current conduction through
said ñrst transistor through a circuit having low im
elements with its collector element> connected to one ter
minal of said capacitor, its emitter element connected to
a potential positive relative to they potential of the emitter
element of said second transistor, and its base element
pedance _whereby the current conduction through said 10 connected to said receive` hub whereby a double space on
said receiveV hub causes said third transistor to conduct
lsecond transistor is eiîective to override the signal on
and thereby change the charge on said capacitor to pre
the send hub in the ycourse of controlling current con
vent said second transistor from being in a conductive
duction in said first transistor;and a second circuit means
including a rectifier, resistance and capacitorconnected
to said second transistor for controlling the current con
duction through said second transistorgthe charge on said
>condenserchanging relatively quickly when a space sig
condition. `
nal is present on said receivingieg to effect a change in
the conduction condition of said second transistor, and
'changing much more slowly when a'rnark signal follows 20
the >space signal to provide a delay equal to approximately
one pulse length of the telegraph code beingV transmitted
before eiîecting a further change in the current conduc
tion condition of said second transistor.
6. The repeater unit as deiìned in claim 5 wherein one 25
terminal von said capacitor is connected Vto the base ele
ment of said second transistor through a paral‘rel circuit
9.- The repeater unit as defined in claim 8 wherein the
_ connection between thebase element on said third tran
sistor and said receive hub comprises a voltage divider
and diode to increase the speed of response of said tran
sistors> to enable full duplex operation.
~ y» References Cited in the tile of this patent
Rea __________ __` ____ __ June 26, 1951
Rea ________________ __ Aug. 19, 1952
Rea ________________ __ Sept. 30, 1952
Davey ______________ __ Apr. 28, 1953
comprising a resistance and a diode, the diode being
' ,poled soìthat leakage current that flows from the col
Radio Engineering, by F. E. Terman;
lector to base elements at high temperatures causes in
McGraw-Hill Book Co., fourth edition, copyright 1955,
suiiicient voltage drop across said resistance to change
pages 632, 633, 777-781, 795.y
' the conduction condition ~of said second transistor.
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