US1898516A - Calling circuit - Google Patents

Description

Feb. 21, 1933. H. B. ARNOLD ET AL CALLING C IRCUIT Filed April 17, 1930 QQEQQQSE Q Q m.

QM Km QMQEUQ M 3+ Q Q IIHI' g Q HB. ARA/01.0 wvavrag: LIB. cooks 7% 6%a Z ATTORNEY Patented Feb. 21, 1933 UNITED STATES PATENT OFFICE HEN RY B. ARNOLD ANID LEIGI-I'ION B. COOKE, OF NEW YORK, N. Y., ASSIGNORS TO WEST- ERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK; N. Y., A CORPORATION 01? CF:

NEW YORK CALLING CIRCUIT Application filed April 17, 1930. Serial No. 445,077.

This invention relates to communication systems and particularly to calling circuits for power line carrier-current telephone systerms.

5 One objectof the invention is to provide a communication system that shall effect selective calling between stations by calling circuits under the control of a telephone dial switch having pulsing contacts which may be initially either in a closed or open position.

Another object of the invention is to provide a power-line carriercurrent system effecting communication in both directions by modulated currents within the same frequency band that shall have selective calling circuits under the control of a telephone dial switch'having pulsing contacts which may be initially either in a closed or open position.

A further object of the invention is to provide a power line carrier-current system that shall effectselective calling between stations by a code signal preceded by a prolonged calling impulse and that shall have the calling circuits controlled during transmission of the code signal by a telephone dial switch having pulsing contacts which may be initially either in a closed or open position.

In a power line carrier-current telephone system it is desirable to limit the frequency range of the modulated currents employed to a narrow range by reason of the transmission characteristics of the power line. In the communication'system disclosedin the a patent to C. N. Nebel #1,733,553 dated October 29, 1929, communication in both direc tions is effected bymeans of modulated currents within the same frequency range. In 40 the present invention which is applied to a system of the type disclosed in the Nobel patent, calling between stations is efiected by carrier-current modulated with impulses of voice frequency current and within the same 5 frequency range as the currents employed to communicate between stations. V7 hen carrier-current modulated with impulses of voice frequency current is employed for call ing purposes, means must be employed to prevent operation of the calling selectors at the signal stations by means of the communication currents.

In the present invention the calling of a distant station is effected by a signal comprisinga prolonged impulse followed by a code signal of carrier-current modulated with impulses of voice frequency current. The system disclosed in the above mentioned Nebel patent is employed to disclose the present invention. The calling impulses employed for calling purposes are modulated and demodulated in the manner disclosed in the Nebel patent. At the calling station an oscillator having a frequency within the voice frequency range is controlled by a pulsing relay in accordance with the calling signal to be transmitted. Normally when the pulsing relay is released, the calling oscillator is connected to the transmitting channel of the associated signal station. {79

The pulsing relay is controlled by a telephone dial switch and the energization of the calling oscillator is controlled by the telephone switchhook. Upon the removal of the removal of the receiver from the switchhook at said station.

The telephone dial switch, which controls the pulsing relayto transmit acalling code signal over the power line, has the cam member thereof modified in order to transmit a small number of impulses but of relatively longer duration. The cam member, which operates in the customary manner, opens and closes a pair of pulsing contacts at half the speed of the usual operation of such contact members in telephone dial switches. Moreover, the pulsing contact members are left in the position last moved to by the cam mem- 95 ber. Thus the pulsing contact members may be either in closed or open condition when it is desired to transmit a calling signal. Means comprising an off-normal relay and a control relay are provided under the control 1 of the pulsing contacts and the off-normal contacts of the dial switch for governing the pulsing relay to transmit a calling code signal over the power line and for disconnecting the calling oscillator from the power line upon completion of a calling signal. The offnormal relay and the control relay insure the operation of the pulsing relay in accordance with the operation of the dial switch irrespective of whether the pulsing contacts of the dial switch are initially in the closed or open position.

The circuits for operating the calling selector at a called station are very similar to the circuits disclosed in the application of L. B. Cooke, Serial No. 443,639, filed April 12, 1930. t the called station a relay has the contact members thereof in circuit with two slow operating relays. The slow operating relays are controlled by the prolonged impulse preceding a calling code signal so that the relay connected to the slow operating relays may operate a selector magnet through he contact members of the slow operating relays when the code signal following the prolonged impulse is received. Upon the operation of the calling selector at the called station means is provided for insuring the removal of the calling oscillator at such station from the power line.

The single figure in the accompanying drawing is a diagrammatic view of a signaling system constructed in accordance with the invention.

Referring to the drawing a signal station having a transmitting channel 1 and a receiving channel 2 is connected to a power line comprising conductors 3, 4 and 5 by means of a coupling filter 6. The coupling filter may be of any simple type and preferably similar to the coupling filter disclosed in the above mentioned patent to Nebel. The transmitting channel 1 is provided with two modulators 7 and 8 and the receiving channel is provided with two demodulators 9 and 10. The modulators in the transmitting channel and the demodulators in the receiving channel are similar in construction and operation to like parts disclosed in the before-mentioned patent to Nebel.

An operators telephone set comprising a receiver 11 and a transmitter 12 is connected to the transmitting channel 1 and the receiving channel 2 by means of a suitable hybrid coil 13. The switchhook of the operators set controls an auxiliary switch 14 for governing the calling circuits in a manner to be described hereinafter. A calling oscillator 15 which is preferably of the thermionic type produces a current having a frequency within the voice frequency range and is normally connected across the transmitting channel 1. The connection of the oscillator 15 to the transmitting channel is controlled by means of a pulsing relay 16. The pulsing relay 16 is provided with two switch members 17 and 18 and two operating coils 19 and 20.

A modified telephone dial switch 21 is provided for controlling the operation of an olfnormal relay 22 and a control relay 23 to govern the operation of the pulsing relay 16. The dial switch 21 is provided with the usual pulsing contacts 24 and ofi -normal contacts 25. The pulsing contacts 24 in place of being controlled by the customary figure 8 cam member, are controlled by a cam member 26 shown in the drawing. The cam member 26 is operated in the customary manner and opens and closes the pulsing contact at half the speed of the usual operation of the pulsing contacts by the figure 8 cam member.

The selectors provided in the system are operated by an odd number of impulses and preferably 17 impulses are required in the code signal. On the 17th impulse it will be noted that the cam member 26 would be in a position opposite to the position from which it started. Accordingly, the pulsing contacts may be left either in an open or closed position at completion of the calling signal. Inasmuch as the oscillator 15 must always be removed from the transmitting channel during conversation between stations special means must be provided for insuring the removal of the oscillator from the transmitting channel at the completion of a calling signal irrespective of the position of the pulsing contacts. Moreover, means must be provided to insure the transmission of a correct code signal irrespective of the initial position of the pulsing contacts. The oilnormal relay 22 and the control relay 23 in sure the correct operation of the pulsing relay 16 in a manner to be hereinafter described. The off-normal relay 22 is provided with two coils 2'? and 2S and two switch members 29 and 30. The control relay 28 is provided with two coils 31 and 32 and three switch members 33, 34 and 35.

The receiving channel 2 is connected by a transformer 36 to a suitable rectifier 37 which in turn is connected to a receiving relay 38.

The receiving relay controls the operat-ion of two slow relays 39 and 40 and a selector magnet 41. Selector magnet 41 operates a selector 42 which controls a relay 43. The selector 42 is of the type disclosed in the patent to J. C. Field #1343256 dated June 15, 1920. The relay 43 is provided with a switch member 44 for completing a circuit from a battery 45 to the calling bell 46 and a switch member 47 for establishing a holding circuit from a battery 48 to the coil of the relay. The relay 48 is also provided. with a switch member 49 for completing a circuit from a battery 50 through a coil of relay 51.

Assuming the dial switch 21 to be in the position shown on the drawing with the pulsing contacts 24 in an open position and it is desired to selectively call a distant station, the receiver 11 is first removed from the switchhook. Upon removal of the receiver from the switchhook the switch 14 is operated for completing the circuit from the battery 59 to operate a filament relay 56. The filament relay '56 completes a circuit from a battery 48 for energizing the oscillator 15. The oscillator 15 is normally connected across the transmitting channel 1 by means of the switch member 18 of the pulsing relay 16. Carrier current is modulated with the prolonged impulse from the oscillator 15 by means of the modulators 7 and 8 in the manner described in the above mentioned patent to Nobel. Thus an initial prolonged impulse is transmitted over the power line to the distant called station.

Upon operation of the dial switch 21, the off-normal contacts 25 complete a circuit from the battery 59 for operating the 011- normal relay 22. The circuit completed by the off-normal contact may be traced from battery 59 through the switch 14, elf-normal contacts 25, coil 27 of the ofi-normal relay 22, switch member 33 of the control relay 23 and ground return to the battery 59. Upon operation of the olf-n'ormal relay 22 a circuit is completed for directly operating the pulsing relay 16 in accordance with the opening and closing of the pulsing contacts 24. The operating circuit for the pulsing relay may be traced from the battery 59 through the switch 14, pulsing contacts 24, switch member 30 of the o'li-normal relay 22, coil 20 of the pulsing relay 16 and ground return to the battery 59. The switch member 18 of the pulsing relay controls the connection of the oscillator 15 to the transmitting channel 1 in accordance with the code signal to be transmitted to the distant station. Switch member 17 completes a circuit from battery 61 through the selector magnet at the calling station to operate the selector at the calling station in accordance with the code signal being transmitted. Upon transmission of the 17th pulsingimpulse, which is the final impulse, the pulsing contacts 24 are closed to operate the pulsing relay 16 and insure the removal or the oscillator 15 from the transmitting channel 1 as is necessary when conversation talres place.

At the distant station, the prolonged impulse and the code signal transmitted by the dial switch are demodulated by the demodulators 9 and 10 and then rectified by the rectifier 37 for operating the receiving relay 38. The prolonged impulse operates the relay 38 a suflicient time to efiect operation or" the slow relays 40 and 39. The slow relays 39 and 40 complete a circuit for permitting the operation of the selector magnet 41 by the receivin relay 38 according to the received code signal. The selector 42 is operated by the selector magnet 41 for completing a circuit from the battery 48 for operating the relay 43. Upon operation of the relay 43, the switch member 47 establishes a holding circuit, the switch member 44 completes a circuit for operating the bell 46 and the switch member 49 completes the circuit for operating the relay 51. The relay-51 is provided with a switch member 65 for completing the circuit from a battery 66 to effect operation of the pulsing relay 16 and insure disconnecting the oscillator 15 at the called station from the transmitting channel 1. The relay 51 is also provided with a switch member 67 for establishing a holding circuit for the. relay upon removal of the receiver from the switchhook at the called station.

Upon removal of the receiver from the switchhook at the called station,- a circuit is completed by the switch 14 for operating the filament relay 56 to break the holding circuit established through the relay 43. The relay 43 is released to stop operation of the calling bell 46. The relay 51 which controls the circuit through the coil 19 of the pulsing relay 16 is not released at this time by reason of the holding circuit established through the switch member 67. The various relays are returned to normal position upon return of the receiver to the switchhook at both the calling and called stations. At the calling station the return of the receiver to the switchhook breaks the holding circuit which had been established through the coil 28 of the off-normal relay 22. At the called station the return of the receiver to the switchhook breaks the holding circuit established through the relay 51.

If the pulsing contacts of the dial switch 21 are initially in closed position, the removal of the receiver 11 from the switchhook at the calling station will complete a circuit for operating the control relay 23. The circuit completed upon removal of the receiverfrom the switchhook may be traced from the battery 59 through the switch 14, pulsing contacts 24, coil 31 of the control relay 23, switch member 29 and ground return to the battery 59. The relay 23 is operated and a shunt circuit is established across the coil 20 of the pulsing relay 16 to prevent operation of the relay 16 until the pulsing contacts 24 of the dial switch are open. The shunt circuit across the coil 20 may be traced from one terminal of the coil through the switch member 34, pulsing contacts 24, and switch member 35 to the other terminal of the coil 20. Upon separation of the pulsing contacts 24 in accordance with the code signal to be transmitted, a circuit is completed from the battery 59 for energizing the coil 20 of the pulsing relay 16. On transmission of the 17th impulse, the pulsing contacts are opened to insure operation of the pulsing relay 16 and the disconnection of the oscillator 15 from the transmitting channel.

Inasmuch as the same signal is transmitted over the power line to the called station when the pulsing contacts are initially in closed position as when the pulsing contacts are initially in open position there is no difference in the operation at the called station in operating the selector. Upon the completion of conversation between the stations, the replacing of the receiver on the switchhook at the calling station serves to break the holding circuit which had been established from the battery 59 through the coil 32 of the control relay 23. It ma be noticed in the opera tion last described that the oil normal contacts of the dial switch perform no useful function.

Modifications in the system and in the arrangement and location of parts may be made within the spirit and scope of the invention and such modifications are intended to be covered by the appended claims.

lVhat is claimed is:

1. In combination, a power line having telephone signal stations connected thereto, an oscillator, a pulsing relay for controlling the connection of said oscillator to said line circuit, a dial switch having pulsing contacts initially in open or closed position upon start of the switch operation and off-normal contacts, an oil-normal relay operated by said off-normal contacts who the dial switch starts operating with the pulsing contacts in open position, means for locking said oanormal relay under control of the receiver switchhook when operated by the oft-normal contacts, and means controlled by the off-normal relay when energized for operating the pulsing relay according to the operation of said pulsing contacts.

2. In combination, a transmission circuit, an oscillator, a pulsing relay for controlling the connection of'said oscillator to said circuit, a dial switch having pulsing contacts initially in open or closed position upon start of the switch operation, a control relay operated upon removal of the receiver from the switchhook when the pulsing contacts are initially closed, means under control of the receiver switchhook for locking the control relay when operated with the pulsing contacts initially in closed position, and means comprising said control relay for operating the pulsing relay according to the operation of the pulsing contacts upon operation of the dial switch with the pulsing contacts in closed position at the start of the switch operation.

3. In combination, an oscillator initially connected to a transmission circuit, a pulsing relay for interrupting the connection of said oscillator to the circuit, a dial switch having pulsing contacts in open or closed position upon start of the switch operation and oilnormal contacts, said pulsing contacts being opened and closed by alternate dial steps, an

oft-normal relay operated by said off-normal contacts when the dial switch starts opera tion with the pulsing contacts in open position, means under control of the receiver switchhoolr for holding the off-normal relay in operative position, means controlled by the oil-normal relay when energized for operating the pulsing relay according to the operation of said pulsing contacts, a control relay operated upon removal of the receiver from the switchhook when the pulsing contacts of the dial switch are initially in closed position, and means comprising said control relay for operating the pulsing relay according to the operation of the pulsing contacts upon operation of the dial switch with the pulsing contacts in closed position at the start of the switch operation.

4-. In combination, a transmission line, an oscillator for transmitting signals over said line, means comprising a pulsing relay for connecting said oscillator to said transmission line, a dial switch having pulsing contacts initially in an open or closed position and so constructed that the pulsing contacts are either opened or closed only by each dial step so that the pulsing contacts are opened during one step of the switch and held open until closed by the next succeeding step, and means controlled by said dial switch irrespective of the starting position of the pulsing contacts for operating said pulsing relay to transmit a code signal of impulses from said oscillator and for disconnecting said oscillator from the transmission line upon completion of the code signal.

5. In combination, a transmission line, an oscillator for transmitting signals over said line, means comprising a pulsing relay for connecting said oscillator to the transmission line, a dial switch having pulsing contacts initially in an open or closed position and so constructed that the pulsing contacts are either opened or closed only by each dial step so that the pulsing contacts are opened dur-' ing one step of the switch and held open until closed by the next succeeding step, and means comprising an oil-normal relay operated when the pulsing contacts are initially open and control relay operated when the pulsing contacts are initially closed and cooperating with said dial switch irrespective of the starting position of the pulsing contacts for operating said pulsing relay to transmit a code signal of impulses from said oscilla-' tor and for disconnecting said oscillator from the transmission line upon completion of the code signal.

6. In a signal system, a power line having a plurality of signal stations connected thereto, an oscillator at a cal ing station having a frequency within the voice frequency range and initially connected to the power line, means comprising a pulsing relay for controlling the connection of said oscillator to the power line, means for energizing said oscillator upon removal of the receiver from the .switchhook at the calling station, a dial switch at a calling station having pulsing contacts which initially may be in an open or closed position, said pulsing contacts being opened and closed by alternate dial steps, and means controlled by said dial switch irrespective of the starting position of the pulsing contacts for varying the connection of said oscillator to the power line according to a code signal of an odd number of impulses and for disconnecting said oscillator from the power line upon completion of the signal.

7. In a signal system, a power line having a plurality of signal stations connected thereto, an oscillator at a calling station, means for energizing said oscillator upon removal of the receiver from the switchhoolr at the calling station and for connecting the oscillator to the power line to transmit a prolonged impulse to the called station, a dial switch at the calling station having pulsing contacts initially in an open or closed position and means controlled by the dial switch irrespective of the .starting position of the pulsing contacts for connecting said oscillator to the power line to transmit a code signal of calling impulses to a called station.

8. In a signal system, a power line having a plurality of signal stations connected thereto, means for communicating between stations by modulated currents within one frequency band, an oscillator at a calling station having a frequency within the voice frequency range, modulating means connected to the power line, a dial switch having pulsing cont acts initially in open or closed position and so constructed that the pulsing contacts are either opened or closed only by each dial step so that the pulsing contacts are opened during one step of the switch and held open until closed by the next succeeding step, and means operated by the dial switch irrespective of the initial position of the pulsing contacts for connecting said oscillator to said modulating means in accordance with a code signal to transmit a calling signal over the power line. 7

9. In a signal system, a power line having a plurality of signal stations connected thereto, an oscillator at a calling station having a frequency within the voice frequency range and initially connected to the power line, means comprising a pulsing relay for selectively controlling the connection of said oscillator to the power line, means for energizing said oscillator upon removal of the receiver from the switchhook at the calling station to transmit a prolonged calling impulse to the called station, a dial switch at the calling station having pulsing contacts initially in an open or closed position and means controlled by the dial switch irrespective of the starting position of the pulsing contacts for operating the pulsing relay to transmit a code signal of calling impulses over the power line.

10. In a signal system, a power line having a plurality of signal stations connected thereto, an oscillator'at a calling station having a frequency within the voice frequency range and initially connected to the power line, a dial switch at a calling station having pulsing contacts which may be normally in an open or closed position, a pulsing relay for controlling the connection of said oscillator to the power line, means operated upon removal of the receiver from the switchhook at the calling station for energizing said oscillator and for preparing circuits to be completed by the dial pulsing and off-normal contacts, and means controlled by said dial switch irrespective of the starting position of the pulsing contacts thereof for operating said pulsing relay to transmit a code signal of impulses from said oscillator.

11. In a signal system, a power line having a plurality of signal stations connected thereto, calling oscillators at said stations each having a frequency within the voice frequency range for transmitting calling signals to the power line, modulating means connected to the power line at said stations for modulating carrier current with voice frequency currents, a pulsing relay at a calling station for selectively connecting the calling oscillator to the modulating means at the station, means for energizing the calling oscillator at the calling station upon removal of the receiver from the switchhook to transmit a prolonged calling impulse to the power line, a dial switch at a calling station having pulsing contacts initially in an open or closed position, and means controlled by the dial switch irrespective of the starting postion of the pulsing contacts for operating the pulsing relay to transmit a code signal of calling impulses over the power line.

In witness whereof, we hereunto subscribe our names this 16th day of April, 1980. Y HENRY B. ARNOLD.

LEIGHTON B. COOKIE.

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