US2376275A

US2376275A - Signaling system

Info

Publication number: US2376275A
Application number: US527915A
Authority: US
Inventors: Rhoads Charles Stanley
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1944-03-24
Filing date: 1944-03-24
Publication date: 1945-05-15
Anticipated expiration: 1962-05-15

Description

y 1945- c. s. RHOADS 6,2

5 IGNALING SYSTEM Filed March 24, 1944 INVENTOR (7. 8.22/4 nads Patented May 15, 1945 S GNALING sYs'rEM i Charles Stanley Rhoads, Albany, lasjsignor Telephone and Telegraph Com to America pally, a corporation of New York 1 s Application March24, 1944, ,Serial No. 527,915 l f dams; (01. 179-13) This invention relates to transmission systems and more particularly to improved arrangements for signaling over such systems.

In certain types 1 of transmission systems, such for example as telephone systems,' it is often de sirable to transmit various types of signals over -a1linel,interconnecting two oflices. One of the methods of accomplishing sucnlsignaling is to connect telegraph apparatus to one side of. a'tele phone line at each of the interconnected ofiices and to use such telegraph apparatus for; the transmission of signals, such forexampleqassupervisory signals, while the line itself isgused for telephone signals. One type of telegraph system,

which might be used in connection with such a composited line, would be alduplegc polar telegraph system havinga sending relay andapolar receiving re'layjat each end of the line and means controlled by the armature of each sending relay n for connecting either ground or one polarity of battery toeither' end of the line to control the receiving relay at the other end. Thearrangement of the invention constitutes animprovement in signaling systems of thi type in that it provides arrangements whereby the telegraph system may be utilized for thesending"ofl vadditional signals, such for example as alarm signals, without any interference with its normal use in transmitting telegraph signals, Hence with the arrangements of the invention it is possible to provide an additional communication channel" between" two oflices with very little change in existing equipment. Other objects and features of the invention will appear more fully from the detailed description; thereof hereinafter I The invention may be morefully understood from theiollowing' description together with the accompanying drawing in the figure of which is shown a circuit diagram embodyinga' preferred formoftheinvention. In the drawing'is shown a line L. For the purpose of illustrating this invention the line L will beassumed tobe a telephone lineinterconnecting two offices. At the left end of the line is a transformer tconnecting the line to the'circuits 3 which might extend to a master office. At the other endof the line is shown a transformer 2 connecting the line to the circuits 4 which might extend to apparatus in a community 'dial oflice. To transmit supervisory signals between two ofilces of this type, it has been the practice to connect a telegraph circuit to one side ofthe vlineiL. In the drawing, the telegraph circuit is h w connectedrto the ring side or the line by meansof the conductors 5 and B.- At the master oifice there would be provided a polar receiving relay 1 and a sending relay 9. The polar receiving relay 1 would have its windings difierentially arranged and one of them would be connected to a balancing artificial line 20. At the com+ munity dial ofiice there would be provided a polar receiving relay ra and a sendingrelaylm The polar receiving :relay 8 would have its windings differentially arranged and oneof them would be connected to a balancing artificialline 2 l L In the arrangements heretofore utilized, the marking and s'pacing contacts of the sending relay 9 and I0 would be connected, respectively, to

ground and to negative battery. such an ar rangement would constitute a form of duplex polar telegraph systemin whichthe operation of either of the sending relays wouldcause a reversal in the direction of current flow over'the line to operate the polar receiving relay at the otherend. of the line. In such an arrangement, when the telegraph circuit was idle, ground would be connected to both of the marking contacts of the sending relays and no it current wouldfiow overthe system, Systems of this type utilized in the past to transmit supervisory signals between a manual ofiice-and a community dial oifice are wellknown the art; For example, if

an operator at the master ofiice'wanted to estab lish a connection to a subscriber in the community dial oftlceshe would insert a cordina trunk jack, not shown, which, by means of circuit 1 I, would operate "the sending relay 9. This would connect negative battery to the line and operate the polar receiving relay Sat the community dial ofiicen This'would causeequipment in the community dial= ofiice to connect trunk equipment to the trunk the manual oflice operator has plugged in on, and would send dial tone to the manual office operator. The manual oifice operator wouldthen plug in to a dialing jack and proceed to dial the number wanted at the com munity dial office. i This operation would cause the relay 9 to function in response to the dialing impulses and send the dial signals over the line to operate the polar receiving relay 8 which, by means of circuit I4, would cause the connec tionto-the desired line to be completed. When .the subscriber at the community dial ofiice answers, equipment in the community dialoflice would (cause the sending relay ill to operate to connect negative batteryto the line to operate the polarreceiving relay 1 atthe master oilice.

This, by means of l the circuit 13, would indicate ;'to the manual ofilce operator that the customer be used for supervisory signals initiated at the community dial oifice. It is pointed out that in the system just described which has been utilized in the past, the marking contacts of each of the sending relays would be connected to ground when the line was idle and accordingly, under such conditions there would be no current flow rent will not be in the proper direction to operate the polar relay 1. It will not operate the polar relay 8 because the currents through its differentially arranged windings will neutralize each other. When the sending relay 9 at the master oflice operates, this will connect the negative battery connected to its spacing contact to the line. As positive battery is connected to the line at the other end, the current through the upper winding of relay 8 will be doubled with respect to the current flowing through its lower winding. Accordingly, the polar relay 8 will be operated by the operation of sending relay 9. When sending relay I I] operates to move its armature to its spacing contact,- negative battery is connected to the line and ground connected to the line at its other end. This will reverse the normal direction of current flow over the line and will cause the polar relay 1 tube operated by the sending relay I8. With such an arrangement current will fiow over the line at all times whether it is idle or whether it is being used to send telegraph signals. At one of the ofiices,

such as the master ofiice, there would be provided a neutral relay l5 which would be'connected in the line and artificial line portions of the telegraph equipment, as shown. The relay I5 is a marginal relay and is so adjusted that it will be held operated by the normal current flowing on the line-either when in an idle condition or in use for signaling. At the other ofl'ice, namely, the community dial ofiice, there would be pro vided a resistance l9 connected in circuit with the armature of the sending relay I0. A normally closed short-circuit l8 around this resistance would be provided. A relay I I would be provided connected in a circuit It. The circuit I 6 might be connected to alarm apparatus which would complete it in the event of equipment failure at the office, or the circuit might be closed by'any desired means, such as a telegraph key. When the circuit I6 is closed and the relay I! operated, the short-circuit about resistance I9 is removed and a connection to ground through a v resistance is established from the armature of the sending relay ID. This will reduce the value circuit will not aiTect the, normal operation of the arrangements for transmitting telegraph signals. When relay [5 releases it closes acircuit through the thermistor 23 and the slow operating relay 22. A thermistor 23 is provided and has answered. The telegraph system would also the relay 22 is made slow to operate so that the momentary release of relay I5 when the armatures of the sending relays are in mid-air, will have no effect. The operation of relay 22 will close a circuit over the right-hand contact of key 21 for the buzzer 24 to indicate to the operator at the master office that the alarm circuit I6 at the community dial office has functioned. The operator may then, through the key 21, operate the lamp 26 and short-circuit the buzzer. When circuit I6 releases and relay l5 again operates, a circuit will be closed over the left-hand contact of key 21 for the buzzer.

While the arrangements of the invention have been disclosed as associated with a telephone line interconnecting two specific types of oflices, it is understood that this is purely for the purposes of illustration and that the arrangements of the invention are capable of being associated with other types of lines. Furthermore, while the arrangements of the invention have been illustrated as used for sending supervisory and alarm signals, it is understood that they are capable of transmitting other varieties of signals.. Accordingly, while the arrangementsrof the invention have been disclosed as embodied in certain specific forms which are deemed desirable, it is unly arranged windings, two sending relays each having its armature connected to the apex of the differentially arranged windings of its associated receiving relay, positiv and negative battery connected to the marking and spacing contacts respectively of the sending relay at one of said stations, ground and negative battery connected to the marking and spacing contacts respectively of the other of said sending relays whereby current will flow over said line at all times, means' at either end of said line for reversing the direction of current through the polar relay at the other end to cause its operation,- a relay included in one end of said line, said relay being marginal and adjusted so that it will be held operated by the normal current flow existingon "said line, and means at the other end of said line for reducing the normal current flow existing onsaid line to release said last mentioned relay without aiiecting the operation of said polar relays.

2. A line, sending relay and polar receiving relays so associated with said line that current flow will exist on said line when it is inidle condition or when a polar receiving relay is being operated by a sending relay at the other end of the line, a marginal relay in one end of said line so adjusted as to be held operative by; the normal currents flowing over the linewhen-it isvidle or when said polar receiving relays are operated for signaling purposes, a signaling circuit controlled by said marginal relay, and means at the other end of said line for reducing the current flow existing on said line at any time whereby said marginal relay may be released, said polar r 2,376,275 receiving relays being adjusted so that they will operat on said reduced current.

3. Aline, sending relays and polar receiving relays so associated withsaid line that current flow will exist on said line when it is in idle condition or when a polar receiving relay is, being operated by a sending relay at the other end of the line, a marginal relay in one end of said line so adjusted as to beheld operative by the normal currents flowin over the line when it is idle or circuit for opening the short circuit aroundsaid resistance whereby the current flow on the line will be sufliciently reduced so that said marginal a relay will be released but the operation of said polar receiving relays will not be affected.

current will flow thereoverwhen said circuit is] i idle or when said circuit is being utilized for the transmission of telegraph signals, a marginal relay associated with one end of said telegraph circuit, said relay being so adjusted that it will be held operated by the normal currents flowing in said telegraph circuit, a slow operate relay controlled by said marginal relay, an alarm circuit controlled by said slow operate relay, means at the end of said line distant from said marginal relay for varying the resistance of the telegraph f circuit thereat whereby the current flow over the line will be reduced so that said marginal relay I will be released, and an alarm circuitffor coning a neutral marginalrelay connected in the 4. A transmission line, atelegra'ph circuit connected to one side of said line at each endthereof, saidtelegraph circuit being so arranged that trolling said last mentioned means.

5. A duplex polarential telegraph system havline and artificial line circuits at one end thereof,

said relay being adjusted to be held in operated condition by the currents normally flowing at all times over said system, and means at the other end thereof to vary the value of saidcurrents to I control said relay.

CHARLES STANLEY RHOADS.