Communication facility integrity checking arrangement

Claim 2

An arrangement for verifying the integrity of an interoffice communication channel connecting a first terminal to a second terminal comprising: means in said first terminal actuated by a receipt of a first check signal from a checking circuit selectively connected thereto for sending a first integrity verification signal over said interoffice channel to said second terminal, means in said second terminal actuated in response to a receipt of said first verification signal from said first terminal for transmitting thereto a second verification signal of predetermined duration to complete said interoffice integrity verification, and means actuated by a receipt of said second verification signal and deactuated upon the expiration of said predetermined duration for delaying the transmission of a second check signal to said checking circuit until said interoffice integrity verification has been completed to thereafter effect the disconnection of said checking circuit.

Claim 3

The arrangement in accordance with claim 1 further comprising: supervisory relay means included in said first terminal and actuated by said receipt of said first check signal for indicating the receipt thereof from said checking circuit to actuate said sending means, and a pair of differential relays included in said delaying means for controlling the operation of said supervisory relay means and for effecting said disconnection of said checking circuit after the said predetermined duration.

Claim 4

The arrangement in accordance with claim 2 wherein said second terminal further includes; means included in said transmitting means actuated upon the receipt of said first verification signal for applying a signal of given polarity to said interoffice connection to effect a transmission of said second verification signal for said predetermined duration, timing means operated upon the receipt of said first verification signal and released upon the expiration of said predetermined duration for generating a time interval having said predetermined duration, and means included in said transmitting means operated in response to the release of said timing means after said expiration of said predetermined duration for reversing the polarity of said signal of given polarity to complete said transmission of said second verification signal and thereafter to effect said disconnection of said checking circuit.

Claim 5

In a telephone switching system wherein common control equipment is seized at a first switching office to establish a call over an interoffice connection to a second switching office and is released subsequent to an interchange of signals along a cross-office path between said equipment and the outgoing trunk at said first office selected to serve said call, an arrangement for verifying the integrity of said interoffice connection comprising means included in said outgoing trunk operated in response to the receipt of a first one of said interchange signals from said equipment for thereupon transmitting a seizure signal over said interoffice trunk to said second office, means in said second office responsive to the receipt of said seizure signal for sending a seizure acknowledgement signal of designated polarity to said outgoing trunk, means in said second office operated after a preselected timeout interval for reversing said designated polarity, and means in said outgoing trunk operated only in response to the receipt of said seizure acknowledgment signal of reverse polarity for returning a second one of said interchange signals to effect a release of said equipment.

Claim 6

In a telephone switching system wherein common control equipment is seized at a first switching office to establish a call over an interoffice connection to a second switching office and is released subsequent to an interchange of signals along a cross-office path between said equipment and the outgoing trunk at said first office selected to serve said call, an arrangement for verifying the integrity of said interoffice connection comprising means included in said outgoing trunk operated in response to the receipt of a first one of said interchange signals from said equipment for thereupon transmitting a seizure signal over said interoffice trunk to said second office, means in said second office responsive to the receipt of said seizure signal for sending a seizure acknowledgement signal of designated polarity to said outgoing trunk, means in said second office operated after a preselected timeout interval for reversing said designated polarity, and means in said outgoing trunk operated only in response to the receipt of said seizure acknowledgment signal of reverse polarity for returning a second one of said interchange signals to effect a release of said equipment.

Claim 7

The arrangement in accordance with claim 4 wherein said outgoing trunk further includes: multistate circuit means effective to establish a plurality of operating states of said trunk circuit for inhibiting said returning means from effecting a release of said equipment until said receipt of said reverse polarity acknowledgment signal, said multistate circuit means establishing a first state in response to a selection of said trunk by said equipment for detecting a receipt of said first interchange signal, a second state in response to said receipt of said first interchange signal for operating said transmitting means to send said seizure signal to said second office, a third state in response to the detection of said seizure acknowledgment signal of designated polarity for indicating a receipt thereof, and a fourth state in response to the detection of said seizure acknowledgment signal of reverse polarity for operating said returning means to effect said release of said equipment.

Claim 8

The arrangement in accordance with claim 5 wherein said multistate circuit means comprises: a plurality of bistable memory elements to establish said plurality of operating states of said trunk circuit.

Claim 9

The arrangement in accordance with claim 6 wherein said bistable elements comprise a pair of differential relays and wherein said outgoing trunk circuit further comprises: a busy relay operated in response to said selection of said trunk circuit for the service of said call, first contact means actuated by the operation of said busy relay for operating a first one of said pair of relays and for maintaining released a second one of said pair of relays to establish said first state, a trunk supervisory relay operated during said first state in response to said receipt of said first interchange signal, second contact means actuated by the operation of said supervisory relay for maintaining operated said first of said pair of relays and for operating said second of said pair of relays to establish said second state, and third contact means included in said transmitting means and responsive to the operation of said trunk supervisory relay for applying said seizure signal over said interoffice connection to said second office.

Claim 10

The arrangement in accordance with claim 7 wherein said outgoing trunk circuit further comprises: a signaling relay operated during said second state upon detection of said seizure acknowledgment signal of designated polarity for indicating the receipt thereof and released during said third state upon said receipt of said seizure acknowledgment signal of reverse polarity, fourth contact means actuated by the operation of said signaling relay for releasing said first of said pair of relays and for maintaining operated said second of said pair of relays to establish said third state, and fifth contact means actuated by the release of said signaling relay for maintaining released said first of said pair of relays and for releasing said second of said pair of relays to establish said fourth state.

Claim 11

The arrangement in accordance with claim 8 wherein said returning means comprises: sixth contact means actuated only when said multistate circuit is in said first state for electrically coupling said trunk supervisory relay to said cross-office path to operate said trunk supervisory relay when said first interchange signal is received from said equipment, and seventh contact means actuated only when said multistate circuit is in said second and said third states for further electrically coupling said trunk supervisory relay to said cross-office path and deactuated when said multistate circuit is in said fourth state for electrically decoupling said trunk supervisory relay from said cross-office path to provide said second interchange signal.

Claim 12

The arrangement in accordance with claim 9 wherein said sending and said returning means are included in a line circuit in said second office, said line circuit further including: a line supervisory relay operated in response to the receipt of said seizure signal, a control relay included in said reversing means operated in response to the operation of said line supervisory relay and released in response to the expiration of said timeout interval, eighth contact means actuated by the operation of said control relay for connecting said sending means to said interoffice connection and deactuated upon the release of said control relay, a time delay control circuit triggerable to generate said preselected timeout interval and deactivated upon the expiration thereof, ninth contact means controlled by said control relay for triggering said time delay control circuit, an indicator relay operated upon the expiration of said timeout interval to deactivate said time delay control circuit and to release said control relay, and tenth contact means actuated by the release of said control relay for connecting said reverse polarity signal to said interoffice connection.

Claim 13

The invention in accordance with claim 10 wherein E and M supervisory signaling is employed between said first and said second offices and wherein said seizure and said designated polarity signals have off-hook polarity and said reverse polarity signal has on-hook polarity, the arrangement further comprising: first signal circuit means in said trunk circuit connecting said cross-office path to said interoffice connection for operating said signaling relay upon detection of said off-hook designated polarity and for releasing said signaling relay upon detection of said on-hook reverse polarity, and second signaling circuit means in said line circuit for operating said line supervisory relay upon detection of said off-hook seizure signal.

Claim 14

The arrangement in accordance with claim 4 wherein said reversing means comprises: bistate means actuated by said seizure signal for initiating the duration of said preselected timeout interval and deactuated upon the expiration thereof for terminating said designated polarity signal to send said signal of reverse polarity.

Claim 15

The arrangement in accordance with claim 12 wherein said sending means and said reversing means are included in a line circuit at said second office, said line circuit further including: a line supervisory relay operated in response to said seizure signal to actuate said bistate means, and timing means operated upon the actuation of said bistate initiating means for generating said preselected timeout interval.

Claim 16

The arrangement in accordance with claim 13 wherein said timing means further includes: relay means operated after said preselected timeout interval for indicating the expiration thereof to deactuate said bistate means and thereafter to send said signal of reverse polarity.

Claim 17

An arrangement for verifying the integrity of a communication facility comprising: a plurality of terminal circuits, a switching network, common control means for establishing a channel across said switching network between a first and second one of said terminal circuits, said communication facility directly connecting said second terminal circuit with a third one of said terminal circuits, continuity checking means connected to said channel for thereacross exchanging check signals on a timeout basis with said second terminal circuit to test the continuity of said channel and released from said channel upon completion of said exchange of check signals, means in said second terminal circuit actuated by the receipt of a first one of said check signals from said continuity checking means for sending a seizure signal to said third terminal circuit over said facility, means in said third terminal circuit responsive to the receipt of said seizure signal for returning an acknowledgement signal of prescribed duration to said second terminal circuit, and means at said second terminal circuit actuated in response to said common control means controlling an establishment of said channel for inhibiting a sending of a second one of said check signals to said continuity checking means until after said acknowledgment signal has been received for said prescribed duration to allow said release of said common control means when said continuity is verified and to prevent said channel from remaining unnecessarily established upon the occurrence of a continuity check failure.

Claim 18

An arrangement for verifying the integrity of a communication facility comprising: a plurality of terminal circuits, a switching network, common control means for establishing a channel across said switching network between a first and second one of said terminal circuits, said communication facility directly connecting said second terminal circuit with a third one of said terminal circuits, continuity checking means connected to said channel for thereacross exchanging check signals on a timeout basis with said second terminal circuit to test the continuity of said channel and released from said channel upon completion of said exchange of check signals, means in said second terminal circuit actuated by the receipt of a first one of said check signals from said continuity checking means for sending a seizure signal to said third terminal circuit over said facility, means in said third terminal circuit responsive to the receipt of said seizure signal for returning an acknowledgement signal of prescribed duration to said second terminal circuit, and means at said second terminal circuit actuated in response to said common control means controlling an establishment of said channel for inhibiting a sending of a second one of said check signals to said continuity checking means until after said acknowledgment signal has been received for said prescribed duration to allow said release of said common control means when said continuity is verified and to prevent said channel from remaining unnecessarily established upon the occurrence of a continuity check failure.

Claim 19

The arrangement in accordance with claim 15 wherein said acknowledgment signal comprises a first reply signal of given polarity and a second reply signal of opposite polarity and wherein said means at said third terminal circuit comprises: means for transmitting said first reply signal to said second terminal circuit, a timing circuit triggered upon the receipt of said seizure signal and released after the expiration of said prescribed duration, and means responsive to said release of said timing circuit for terminating said first reply signal and for transmitting said second reply signal to said second terminal circuit.

Claim 20

The arrangement in accordance with claim 16 wherein said second terminal circuit includes: a plurality of binary memory elements, and circuit means interconnecting said memory elements for establishing a plurality of operating modes of said second terminal circuit to actuate said sending means and to deactuate said inhibiting means.

Claim 21

The arrangement in accordance with claim 17 wherein each of said memory elements is a differential relay and wherein said means for inhibiting includes: first relay contact means connected to said channel when said circuit means is in a first one of said operating modes for maintaining said first check signal from said checking means until said sending of said second check signal, and supervisory relay means connected to said first contact means and responsive to the receipt thereover of said first check signal for operating said circuit means to a second one of said modes indicating a receipt of said seizure signal.

Claim 22

The invention in accordance with claim 18 wherein said second check signal is generated by the disconnection of said supervisory relay from said channel, the arrangement further comprising: second relay contact means in said inhibiting means connected between said channel and said supervisory relay means and bridging said first contact means actuated when said circuit means is in said second operating mode for further maintaining an application of said first check signal to said supervisory relay means, and signal detecting means operated upon the receipt of said first reply signal for indicating the receipt thereof to place said circuit means in a third operating mode and released upon the receipt of said second reply signal of reverse polarity for specifying the receipt thereof to place said circuit means in a fourth operating mode and to then disconnect said supervisory relay from said channel.

Claim 23

An arrangement for verifying the integrity of a communication facility between a trunk circuit in a first switching office and a line circuit in a second switching office and comprising: a W-Z relay circuit in the trunk circuit of the first office wherein both said W and said Z relays are differentially wound relays, means for placing said W-Z relay circuit in a first state on selection of the outgoing trunk circuit in the first office, means for placing said W-Z relay circuit in a second state on seizure and activation of supervision of said trunk circuit in said first office, means for placing said W-Z relay circuit in a third state on receipt of an off-hook seizure acknowledgment signal from said line circuit of the second office, and means for returning said W-Z relay circuit to its initial state on receipt of a subsequent on-hook signal of predetermined duration from said line circuit of the second office.

Claim 24

An arrangement for verifying the integrity of a communication facility between a trunk circuit in a first switching office and a line circuit in a second switching office and comprising: a W-Z relay circuit in the trunk circuit of the first office wherein both said W and said Z relays are differentially wound relays, means for placing said W-Z relay circuit in a first state on selection of the outgoing trunk circuit in the first office, means for placing said W-Z relay circuit in a second state on seizure and activation of supervision of said trunk circuit in said first office, means for placing said W-Z relay circuit in a third state on receipt of an off-hook seizure acknowledgment signal from said line circuit of the second office, and means for returning said W-Z relay circuit to its initial state on receipt of a subsequent on-hook signal of predetermined duration from said line circuit of the second office.

Claim 25

An arrangement for delaying the release of a sender in a toll office until verification of seizure of a line circuit in a distant office to check the integrity of the interoffice communication facility comprising a memory circuit at the toll office having four states, means for placing said memory circuit in a first state upon selection of an outgoing trunk circuit at the toll office, means for placing said memory circuit in a second state on transmission of a seizure signal over the trunk circuit to the distant office, means responsive to a seizure acknowledgment signal having a prescribed duration from the line circuit of the distant office for placing said memory circuit in a third state, means responsive to receipt of an on-hook signal from the line circuit of the distant office after said prescribed duration for returning said memory circuit to its initial state, and means responsive to the return of said memory circuit to its initial state for opening a cross-office path in said toll office to effect release of the sender therefrom.

Claim 26

An arrangement for delaying the release of a sender in a toll office until verification of seizure of a line circuit in a distant office to check the integrity of the interoffice communication facility comprising a memory circuit at the toll office having four states, means for placing said memory circuit in a first state upon selection of an outgoing trunk circuit at the toll office, means for placing said memory circuit in a second state on transmission of a seizure signal over the trunk circuit to the distant office, means responsive to a seizure acknowledgment signal having a prescribed duration from the line circuit of the distant office for placing said memory circuit in a third state, means responsive to receipt of an on-hook signal from the line circuit of the distant office after said prescribed duration for returning said memory circuit to its initial state, and means responsive to the return of said memory circuit to its initial state for opening a cross-office path in said toll office to effect release of the sender therefrom.