US2428028A - Electrical signaling system - Google Patents

Electrical signaling system Download PDF

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US2428028A
US2428028A US478700A US47870043A US2428028A US 2428028 A US2428028 A US 2428028A US 478700 A US478700 A US 478700A US 47870043 A US47870043 A US 47870043A US 2428028 A US2428028 A US 2428028A
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relay
code
relays
circuit
telephone
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US478700A
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Joly Leon
Andres Louis Charles
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International Standard Electric Corp
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International Standard Electric Corp
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M11/00Telephonic communication systems specially adapted for combination with other electrical systems
    • H04M11/04Telephonic communication systems specially adapted for combination with other electrical systems with alarm systems, e.g. fire, police or burglar alarm systems

Definitions

  • the present invention refers to signaling systems and particularly to signaling systems for the remote transmission of codes capable of being used for purposes of remote metering, remote control, remote indication, and the like, by means of an ordinary telephone line which can also be used for the transmission of telephone calls and messages.
  • One object of the invention is to provide a.
  • code signaling system of this type in which the codes consist of direct currents of differential intensities and polarities, and are decoded at the receiving station by means of suitably arranged and designed decoding relays.
  • Another object of the invention is to provide means at each receiving station to send back to the transmitting station an acknowledge signal at the end of the transmission of each code, each transmitting station having means for receiving, decoding and registering the acknowledge signal.
  • Still another object of the invention is to branch -a telephone speaking circuit, and if desired also a ringing circuit to the line, preferably in such a manner that the decoding relays are not influenced by any speaking or ringing currents transmitted.
  • FIG. 1- is a wiring diagram of one station of a signaling system according to the invention
  • Fig. 1A illustrates a modification of the system according to Fig. 1;
  • Fig. 2 is a wiring diagram of one station in a system including automatic means at each' sta tion for sending back an acknowledge signal and alsomeans for receiving and registering such acknowledge signal.
  • Fig. 3 is a diagram of a telephone circuit to be used in the signalling system according to Fig. 1 if the calling is effected by code;
  • Fig. 3A illustrates a modification of the telephone circuit according to Fig. 3.
  • Fig.4 is a wiringdiagram of a similar telephone circuit including means to effect ringing with an alternatingcurrent.
  • Relays A and B are connected in a decoding circuit loop to one of the wires of line L and relays C and D to the other wire over contacts I and 3 of a reversing switch L1 in the normal, receiving,
  • the decoding relays are polarized, either by their design or, as shown in Fig. 1', by the connection in parallel to their windings of unidirectional conductors R, such as dry rectifiers, or else as shown in the alternative of Fig. 1A, by the placing in series with theirwindings of unidirectional conductors R.
  • Two relays A and C are arranged to'operate when a current of certain value passes through their windings and the remaining relays B and D, when a current of a different value, c. g., of higher value passes through them.
  • the four code signals used are indicated in the drawing by the graphical representation bracketed under wires a and b, Whichare connected to the normally open contacts 2 and 4 of the reversing switch I1.
  • the four codes consist of currents of different polarities and of different strengths.
  • code-sending wires a and 1) maybe connected to a'battery by means of a code selecting switch (not shown) whereby the battery can be connected, either with one polarity or with an inverse polarity, to the wires may not be inserted betweenthe battery and wires a and b according to the positions of the code selecting switch.
  • the code selecting switch When the code selecting switch has closed a circuit a, b in one of its operating positions, for example to the positive battery for wire a and to the negative for wire b without the insertion of any resistances (code 3), and reversing switch 11 has closed contacts 2 and 4, disconnecting at the same time relays A, B,'C, D at the transmitting station from line L, the battery loop is closed 3 over line L and contacts I and 3 of the receiving station to the four relays A, B, C, D of the receiving station.
  • One of these relays (for instance D), which is sensitive to the strength and the direction of the current thus transmitted, operates and, through its contact, records the code transmitted.
  • each of 5 the normal decoding relays A to C is associated with a relay A to C each having one terminal thereof connected through a front contact of the corresponding A to C relay to one of the terminals of a battery, while the other terminal of each relay A to C is connected to the other terminal of thebattery.
  • one of the relays AKB? or C operates'at the receiving stati'oni'deperrding upon whi'ch"on'eof the relays A, B or C has been energized by the code trans- C will also operate, so that the code is here repre-" niitted.
  • relays A, B and sented by the simultaneous operation of relaysq and D in distinction from the code'represented by the operation of relay 0 alone.
  • means may be provided at the receiving station to send backtojthe sending sta-" tion an acknowledge signal at the end of'ieach code transmitted.
  • An example of a station circuit C are connected in parallel to the winding of a relay D which is thus always energized regardless of which one of the relays A, B or C is operated. "At its front contact, relay D prepares theienergizin g circ t; of an acknowledge relay D" having back'contacts which are normally inserted in: the wires of line L.
  • relay D is assigned exclusively to the controlnf the code reception and it'sfront contact-is connected to an audible orvisible indicating device or electric A, B and C that had operated at the receiving stationr'eleases and at itsback contaCtmomern tarilyclose'sthe"energizing circuit of'lthe acknowl edge' relay Df"across*the front contactof relay locking-device which in'ay have-"an e'nergizing D 'which remains temporarily closed, Relay D"- circuit controlled by'a'nornially open contact '5 of the reversing swi'tch-I When relay D closes, positive battery' is applied to ihdic'ating device E.
  • Indicator'E may respond thereto in any suitable manner, aswell known in the art, suchas by ringing a bell,"show'ing-'a-light or other visible' signal, 'or 'disp'laying*"any type of temporary sig-' nal which may 'be distinguishable.
  • "Indicating device El ' maylalternativelybe energized by positivebattery being applied thereto through the closure of'switch5when the station is thrown into the transmitting positionfas described in thefollowing paragraphz Whmth reversing switch I1 is operated at the sending station, the indicating'br 'reeoidihg is o "Th vcircuits then l lef r f y.
  • telephone speaking circuit ATI may be branched to the 'line L, as shownin the diagram of Fig. 3;"
  • the front contacts't, 9 of thereversing-switch'h are-connected in parallel to one terminal of a, telephone ringing current generator a G of any suitable type.
  • the reversing switch I2 may consist either of a key-connecting the ringing current source' G to the line L or of a relay actuated by a cam contact of a hand generator G. 1
  • the call is received at the called station by a hell or" a lamp panel S that is normally placed 7 in' circuit with ground return by the back conposition, i. e., while reversing switch I1 is not operated.
  • the code relays are not traversed by any current during the transmission of the telephone ringing or speaking current because the two line wires remain at the same electric potential. Further, since the return of the telephone circuit is provided by the ground, telephone conversation and ringing always remain possible, even if one of the wires of line L should be broken.
  • a signaling system for the transmission of electric code signals between two identical stations connected by a two conductor line each of said stations comprising signal transmitting equipment including two output wires, and means to supply to said output wires various direct currents corresponding, respectively, to the signal codes to be transmitted, each of said currents having a characteristic intensity and a characteristic flow direction
  • signal receiving equipment including two input wires, a decoding circuit connected to said input wires and containing for each signal code which may be received a normal decoding relay being designed and arranged in said decoding circuit to respond only to current of an intensity and flow direction corresponding to that of the associated signal code, a reversible switch to connect said line conductors normally to said input wires and optionally to said output wires, and control equipment including means to supply to said line conductors a control code of a characteristic current intensity and flow direction, a control relay responsive to said control code in said decoding circuit, an indicator controlled by a front contact of said control relay, 2.
  • slow release relay a circuit passing current through said slow release relay upon exclusive energization of any one of said normal decoding relays, an acknowledge relay, an energizing circuit for said acknowledge relay containing in series a front contact of said slow release relay and back contacts of all said normal decoding relays, and means controlled by said acknowledge relay to connect the line conductors to said control code supply means while disconnecting them from said input wires of the receiving equipment.
  • a signaling system including for each normal decoding relay an auxgieetes circuit and to the de iliary relay, eachauxiliary;relay beiiig adaptd T to be energized over arront contact of the corresponding normal decoding relay-,said circuit for passing current through-said slow release relay *comprising for each of said normal decoding code signals having the same polarity but having different intensities so that only a single one of said auxiliary relays will respond to a pre-determined code signal and actuate said slow re lease relay.
  • a signaling system including an energizing circuit for said indi cator, a contact in said indicator energizing circuit controlled by said reversible switch to en-- ergize the indicator and to produce anindication when said switch is operated to connect the line conductors to said output wires, the front contact of said control relay operating said indicator to cancel such indication.
  • a signaling system for the transmission of electric code signals and the exchange of telephone messages between two identical stations connected by a two-conductor line, each of said stations comprising signal transmitting equipment including two output wires, and means to supply to said output wires various direct currents corresponding, respectively, to the codes to be transmitted, each of said currents having a characteristic intensity and a characteristic current flow direction, signal receiving equipment including two input wires, a decoding circuit connected to said input wires and containing for each code which may be received a decoding relay, each decoding relay being designed and arranged in said decoding circuit to respond only to a current of an intensity and flow direction corresponding to that of the associated code, a
  • reversible switch to connect said line conductors normally to said input wires and optionally to said output wires, and telephone circuits including telephone equipment and two branch conductors for said equipment each containing a condenser, said branch conductors being connected in parallel to the input wires of said receiving equipment.
  • a signaling system as claimed in claim 4, in which said telephone equipment is connected serially in a loop across said branch conductors.
  • a signaling system as claimed in claim 4, in which both said branch conductors are connected in parallel to one terminal of said telephone equipment, the other terminal of which is grounded.
  • each station includes a generator for alternating ringing current, one terminal of said generator being connected to ground, a second

Description

Sept. 30, 194 7. JQLY ET 2,428,028
ELECTRICAL SIGNALING SYSTEM I Filed March 10 1943 2511-6815-511961; l
(MARGINAL RELAY 4 Coca: odi ons I I D"; L 7
POLAR\ZE D MARGINAL RELAY INVENTORS lieu J94Y (nu/3C 01mg BY I ATroR EY v Sept. 30, 1947.
L. JOLY ET AL ELECTRICAL SIGNALING "SYSTEM Filed Mrch 10, 1943 2 shee s-sneak 2 INVENTORS Zia/r JOLY tau/s Cflnwgss BY I gig? I ATTORNEY Patented Sept. 30, 1947 Leon Joly and Louis Charles Andres, .Paris, France, assignorsto International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application March 10, 1943, Serial No. 478,700 In France May 28, 1941 'The present invention refers to signaling systems and particularly to signaling systems for the remote transmission of codes capable of being used for purposes of remote metering, remote control, remote indication, and the like, by means of an ordinary telephone line which can also be used for the transmission of telephone calls and messages.
One object of the invention is to provide a.
code signaling system of this type in which the codes consist of direct currents of differential intensities and polarities, and are decoded at the receiving station by means of suitably arranged and designed decoding relays.
Another object of the invention is to provide means at each receiving station to send back to the transmitting station an acknowledge signal at the end of the transmission of each code, each transmitting station having means for receiving, decoding and registering the acknowledge signal.
Still another object of the invention is to branch -a telephone speaking circuit, and if desired also a ringing circuit to the line, preferably insuch a manner that the decoding relays are not influenced by any speaking or ringing currents transmitted.
These and other objects are accomplished, ac
cording to the present invention, by the arrangement and combination of elements set forth in' the following description, defined in the appended claims and illustratively exemplified in the accompanying drawings, in which Fig. 1- is a wiring diagram of one station of a signaling system according to the invention;
Fig. 1A illustrates a modification of the system according to Fig. 1;
Fig. 2 is a wiring diagram of one station in a system including automatic means at each' sta tion for sending back an acknowledge signal and alsomeans for receiving and registering such acknowledge signal. I I
Fig. 3 is a diagram of a telephone circuit to be used in the signalling system according to Fig. 1 if the calling is effected by code;
Fig. 3A illustrates a modification of the telephone circuit according to Fig. 3; and
Fig.4 is a wiringdiagram of a similar telephone circuit including means to effect ringing with an alternatingcurrent.
' The equipment of only one of the two con- '7 Claims. 179-2) shown comprises four decoding relays, A, B, C, D.
Relays A and B are connected in a decoding circuit loop to one of the wires of line L and relays C and D to the other wire over contacts I and 3 of a reversing switch L1 in the normal, receiving,
position of the latter. The decoding relays are polarized, either by their design or, as shown in Fig. 1', by the connection in parallel to their windings of unidirectional conductors R, such as dry rectifiers, or else as shown in the alternative of Fig. 1A, by the placing in series with theirwindings of unidirectional conductors R. Two relays A and C are arranged to'operate when a current of certain value passes through their windings and the remaining relays B and D, when a current of a different value, c. g., of higher value passes through them.
The four code signals used are indicated in the drawing by the graphical representation bracketed under wires a and b, Whichare connected to the normally open contacts 2 and 4 of the reversing switch I1. The four codes consist of currents of different polarities and of different strengths. For this purpose, code-sending wires a and 1) maybe connected to a'battery by means of a code selecting switch (not shown) whereby the battery can be connected, either with one polarity or with an inverse polarity, to the wires may not be inserted betweenthe battery and wires a and b according to the positions of the code selecting switch.
When the code selecting switch has closed a circuit a, b in one of its operating positions, for example to the positive battery for wire a and to the negative for wire b without the insertion of any resistances (code 3), and reversing switch 11 has closed contacts 2 and 4, disconnecting at the same time relays A, B,'C, D at the transmitting station from line L, the battery loop is closed 3 over line L and contacts I and 3 of the receiving station to the four relays A, B, C, D of the receiving station. One of these relays (for instance D), which is sensitive to the strength and the direction of the current thus transmitted, operates and, through its contact, records the code transmitted. It is evident that in this example, as in the following ones, the four unit figure adopted for the codes is given only as an illustration and that as many codes may be provided as desired by inserting a corresponding number of resistances of different values between thebat'tery and wires a, b through the'c'ode-selectingswitch. At the same time as the operation of relay D, relay 4 and corresponding auxiliary relay are operated, is thought to be fully evident from the circuit shown in Fig. 2.
In the arrangement shown in Fig. 2, each of 5 the normal decoding relays A to C is associated with a relay A to C each having one terminal thereof connected through a front contact of the corresponding A to C relay to one of the terminals of a battery, while the other terminal of each relay A to C is connected to the other terminal of thebattery. As a result, one of the relays AKB? or C operates'at the receiving stati'oni'deperrding upon whi'ch"on'eof the relays A, B or C has been energized by the code trans- C will also operate, so that the code is here repre-" niitted. The front contacts of relays A, B and sented by the simultaneous operation of relaysq and D, in distinction from the code'represented by the operation of relay 0 alone. In order to have assurance atthe sending station that the code signal transmitted 'has' been" recorded correctly, means may be provided at the receiving station to send backtojthe sending sta-" tion an acknowledge signal at the end of'ieach code transmitted. An example of a station circuit C; are connected in parallel to the winding of a relay D which is thus always energized regardless of which one of the relays A, B or C is operated. "At its front contact, relay D prepares theienergizin g circ t; of an acknowledge relay D" having back'contacts which are normally inserted in: the wires of line L.
7 "Relay D? is a slow release relay. Consequently,
when the reversing switch I1 is returned to normal incorporating such means is shown in Figfzf 5 position'at the sending station, that one of relays One of the decoding relays, e. g., relay D, is assigned exclusively to the controlnf the code reception and it'sfront contact-is connected to an audible orvisible indicating device or electric A, B and C that had operated at the receiving stationr'eleases and at itsback contaCtmomern tarilyclose'sthe"energizing circuit of'lthe acknowl edge' relay Df"across*the front contactof relay locking-device which in'ay have-"an e'nergizing D 'which remains temporarily closed, Relay D"- circuit controlled by'a'nornially open contact '5 of the reversing swi'tch-I When relay D closes, positive battery' is applied to ihdic'ating device E. Indicator'E may respond thereto in any suitable manner, aswell known in the art, suchas by ringing a bell,"show'ing-'a-light or other visible' signal, 'or 'disp'laying*"any type of temporary sig-' nal which may 'be distinguishable. "Indicating device El 'maylalternativelybe energized by positivebattery being applied thereto through the closure of'switch5when the station is thrown into the transmitting positionfas described in thefollowing paragraphz Whmth reversing switch I1 is operated at the sending station, the indicating'br 'reeoidihg is o "Th vcircuits then l lef r f y.
' r-; C0de"1312,nSmiSSi0l1.
device Eoperates at this'sam'e' station through the closing of "contact 5, to produce an indication assoon' as a current is sent over lineL through con- 1 tacts- 2 and "At th'efreceiving station; one bf the relays A," B or C is energizedydepending upon the code transmitted. Incoming signals pass through the windings of relays AB, C and D in series' 'an'd causeselective energization thereof, *as already explained" in' iiito'the' receiving station."
'zzat" itsfront'contacts connects to the line over wirese and "f 'a battery of: definite polar"y and voltagevalues to transmit an acknowledge'code The acknowledge code operates at the sending stationthecontrol relay D. In operating, relay .iiDcontrols'at its f'ro'nt contact an operation-of the" 0 acknowledging recordirigbf the code transrnitte d As soon as'relay D of the receiving station releases,it-causes the release of relay 'D' "of"the receivingstationand'relay D of the sending sta-' In addition'to'the code transmission circuits, a
telephone speaking circuit ATI may be branched to the 'line L, as shownin the diagram of Fig. 3;"
in parallel with thedecodingrela'y' circuit at con- 5112301251 and 3 of the reversing switch Iij In this" way, a telephone conversation can take place" when the reversing switchli is init'sjhorn al positionfafter a ringing signal has been trans-f connection-with the descriptionof Fig.1. Re1ays 55 t d; '8- g., by means of one of the signaling A and B 'have back contacts in-series with positive" battery and the windings'of "relays A' and Bfi" Whenasignal having an intensity'be'lowthe marginal response value'of relay'B is're'ceived'relay" codes assignedjto that function.
A will take'batterythrough' the closed contacts gg direct signaling 'eiii eiitfiiip n'e telephone Cir;
of relay B; and'by'the closure of its own contacts I will apply battery to relay Af. A signal having intensity sufficient additionally to actuate relay- B, I will open the circuit through the contacts of relay-A; and additionallywill apply battery 'diwires of lineL should be brokeng" V i Instead or using codgflflfiiflB'i as in the case of the inventionprovides a secondlreversing switchgIz i lliiggel, h aving b'a'ck contacts '6, 1
which' are inserted in series with' backfconta cts apply currentto 'relay w enever a ea ng- I 3 of the reversing switch Ii in thelwires;
in parallel-to the telephone coding circuit: The front contacts't, 9 of thereversing-switch'h are-connected in parallel to one terminal of a, telephone ringing current generator a G of any suitable type.
The reversing switch I2 may consist either of a key-connecting the ringing current source' G to the line L or of a relay actuated by a cam contact of a hand generator G. 1
The call is received at the called station by a hell or" a lamp panel S that is normally placed 7 in' circuit with ground return by the back conposition, i. e., while reversing switch I1 is not operated. The code relays are not traversed by any current during the transmission of the telephone ringing or speaking current because the two line wires remain at the same electric potential. Further, since the return of the telephone circuit is provided by the ground, telephone conversation and ringing always remain possible, even if one of the wires of line L should be broken.
The circuits described may be modified in numerous ways within the scope of the followin claims.
We claim:
1. A signaling system for the transmission of electric code signals between two identical stations connected by a two conductor line, each of said stations comprising signal transmitting equipment including two output wires, and means to supply to said output wires various direct currents corresponding, respectively, to the signal codes to be transmitted, each of said currents having a characteristic intensity and a characteristic flow direction, signal receiving equipment including two input wires, a decoding circuit connected to said input wires and containing for each signal code which may be received a normal decoding relay being designed and arranged in said decoding circuit to respond only to current of an intensity and flow direction corresponding to that of the associated signal code, a reversible switch to connect said line conductors normally to said input wires and optionally to said output wires, and control equipment including means to supply to said line conductors a control code of a characteristic current intensity and flow direction, a control relay responsive to said control code in said decoding circuit, an indicator controlled by a front contact of said control relay, 2. slow release relay, a circuit passing current through said slow release relay upon exclusive energization of any one of said normal decoding relays, an acknowledge relay, an energizing circuit for said acknowledge relay containing in series a front contact of said slow release relay and back contacts of all said normal decoding relays, and means controlled by said acknowledge relay to connect the line conductors to said control code supply means while disconnecting them from said input wires of the receiving equipment.
2. A signaling system, as claimed in claim 1, including for each normal decoding relay an auxgieetes circuit and to the de iliary relay, eachauxiliary;relay beiiig adaptd T to be energized over arront contact of the corresponding normal decoding relay-,said circuit for passing current through-said slow release relay *comprising for each of said normal decoding code signals having the same polarity but having different intensities so that only a single one of said auxiliary relays will respond to a pre-determined code signal and actuate said slow re lease relay.
3. A signaling system, as claimed in claim L including an energizing circuit for said indi cator, a contact in said indicator energizing circuit controlled by said reversible switch to en-- ergize the indicator and to produce anindication when said switch is operated to connect the line conductors to said output wires, the front contact of said control relay operating said indicator to cancel such indication.
4. A signaling system for the transmission of electric code signals and the exchange of telephone messages between two identical stations connected by a two-conductor line, each of said stations comprising signal transmitting equipment including two output wires, and means to supply to said output wires various direct currents corresponding, respectively, to the codes to be transmitted, each of said currents having a characteristic intensity and a characteristic current flow direction, signal receiving equipment including two input wires, a decoding circuit connected to said input wires and containing for each code which may be received a decoding relay, each decoding relay being designed and arranged in said decoding circuit to respond only to a current of an intensity and flow direction corresponding to that of the associated code, a
, reversible switch to connect said line conductors normally to said input wires and optionally to said output wires, and telephone circuits including telephone equipment and two branch conductors for said equipment each containing a condenser, said branch conductors being connected in parallel to the input wires of said receiving equipment. I
5. A signaling system, as claimed in claim 4, in which said telephone equipment is connected serially in a loop across said branch conductors.
6. A signaling system, as claimed in claim 4, in which both said branch conductors are connected in parallel to one terminal of said telephone equipment, the other terminal of which is grounded.
7. A signaling system, as claimed in claim 4, in which each station includes a generator for alternating ringing current, one terminal of said generator being connected to ground, a second
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3466606A (en) * 1962-03-14 1969-09-09 Int Standard Electric Corp Binary data transmission and pulse counter

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1142252A (en) * 1913-04-28 1915-06-08 William E Harkness Remote-control high-potential switch.
US1653130A (en) * 1927-01-04 1927-12-20 Westinghouse Air Brake Co Electropneumatic brake
US1704736A (en) * 1923-10-29 1929-03-12 Union Switch & Signal Co Railway-traffic-controlling apparatus and electrical apparatus suitable for use therein
GB314112A (en) * 1928-03-22 1929-06-24 Siemens Brothers & Co Ltd Improvements relating to electrical signalling systems
US1786805A (en) * 1926-08-14 1930-12-30 Westinghouse Electric & Mfg Co Supervisory control system
US2101209A (en) * 1934-07-21 1937-12-07 American Telephone & Telegraph Signaling system
US2148044A (en) * 1932-05-27 1939-02-21 North Electric Mfg Company Supervisory control system
US2259573A (en) * 1939-03-11 1941-10-21 Union Switch & Signal Co Remote control system
US2321922A (en) * 1940-10-18 1943-06-15 Ibm Automatic meter reading apparatus

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1142252A (en) * 1913-04-28 1915-06-08 William E Harkness Remote-control high-potential switch.
US1704736A (en) * 1923-10-29 1929-03-12 Union Switch & Signal Co Railway-traffic-controlling apparatus and electrical apparatus suitable for use therein
US1786805A (en) * 1926-08-14 1930-12-30 Westinghouse Electric & Mfg Co Supervisory control system
US1653130A (en) * 1927-01-04 1927-12-20 Westinghouse Air Brake Co Electropneumatic brake
GB314112A (en) * 1928-03-22 1929-06-24 Siemens Brothers & Co Ltd Improvements relating to electrical signalling systems
US2148044A (en) * 1932-05-27 1939-02-21 North Electric Mfg Company Supervisory control system
US2101209A (en) * 1934-07-21 1937-12-07 American Telephone & Telegraph Signaling system
US2259573A (en) * 1939-03-11 1941-10-21 Union Switch & Signal Co Remote control system
US2321922A (en) * 1940-10-18 1943-06-15 Ibm Automatic meter reading apparatus

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3466606A (en) * 1962-03-14 1969-09-09 Int Standard Electric Corp Binary data transmission and pulse counter

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