Method and apparatus for idle path search in a time division multiplexed switching network

Claim 2

A pathfinding method of selecting time slots in cyclically recurring frames for a signal path between two selected lines of a digital switching network in which a list in status memory means indicates the busy or idle status of each time slot on one of said selected lines and in which available idle time slots on only the other of said selected lines are encoded with a signal indicating the availability of the time slots, the steps of: identifying the busy or idle status of each time slot on said one line from the list in said status memory means; enabling switching means to provide a signal path between said selected lines during each time slot identified as available on said one line for carrying signals between the lines; detecting an encoded signal carried to said one line from said other line for indicating a time slot available on both of said selected lines; and registering the identity of the last said time slot for use by a procEssor.

Claim 3

A pathfinding method of selecting time slots in cyclically recurring frames for a signal path between selected input and output lines of a network in which available idle time slots on only the input line are encoded with a signal indicating the availability of the time slots and in which a list in status memory means indicates the busy or idle status of each time slot on the output line, the steps of: identifying the busy or idle status of each output line time slot from said list; enabling switching means to provide a signal path between the input line and the output line during each time slot identified as idle on said output line for carrying signals on the input line to the output line; detecting an encoded signal carried to the output line from the input line for indicating a time slot available on both said input and said output line; and registering the identity of the last said time slot.

Claim 4

A pathfinding method of selecting time slots in cyclically recurring frames for a signal path between selected input and output lines of a network in which available idle time slots on only the input line are encoded with a signal indicating the availability of the time slots and in which a list in status memory means indicates the busy or idle status of each time slot on the output line, the steps of: identifying the busy or idle status of each output line time slot from said list; enabling switching means to provide a signal path between the input line and the output line during each time slot identified as idle on said output line for carrying signals on the input line to the output line; detecting an encoded signal carried to the output line from the input line for indicating a time slot available on both said input and said output line; and registering the identity of the last said time slot.

Claim 5

A method as in claim 2 wherein the step of detecting an encoded signal additionally comprises the step of partially testing the continuity of the established signal carrying path.

Claim 6

In a method of selecting idle time slots in cyclically recurring frames for a call signal path between input and output highways of a telephone system in which idle time slots on only the input highway are encoded with an illegal word indicating idle time slots and in which a list in a status memory indicates the busy or idle status of each time slot on the output highway, the steps of: successively identifying the busy or idle status of output highway time slots from said list; enabling gate means to provide a signal path between the input highway and the output highway during each time slot identified as idle for carrying signals on the input highway to the output highway; detecting illegal words carried to the output highway from the input highway for indicating an idle time slot on both said input and said output highway; and registering the identity of the last said time slot for use in establishing a call connection.

Claim 7

In a method of selecting idle time slots in cyclically recurring frames for a call signal path between input and output highways of a telephone system in which idle time slots on only the input highway are encoded with an illegal word indicating idle time slots and in which a list in a status memory indicates the busy or idle status of each time slot on the output highway, the steps of: successively identifying the busy or idle status of output highway time slots from said list; enabling gate means to provide a signal path between the input highway and the output highway during each time slot identified as idle for carrying signals on the input highway to the output highway; detecting illegal words carried to the output highway from the input highway for indicating an idle time slot on both said input and said output highway; and registering the identity of the last said time slot for use in establishing a call connection.

Claim 8

A method as in claim 4 wherein the step of detecting an illegal word additionally comprises the step of partially testing the continuity of the established signal carrying path.

Claim 9

A method as in claim 4 wherein the telephone system comprises input highways and output highways and means selecting an input and an output highway for each call signal and wherein the step of detecting illegal words is independent for each output highway.

Claim 10

In a method of selecting idle time slots in cyclically recurring frames on a selected one of a plurality of input highways and a selected one of a plurality of output highways in a network of highways in a telephone system in which idle time slots on only the input highways are encoded with an illegal word and in which lists in status memory means indicate the time slots which have an idle status on each one of the output highways, the steps of: successively identifying the idle status of time slots on the selected output highway from said list in the status memory means for the selected output highway independently of the lists for each other output highway; enabling means to provide a signal path between the selected input highway and the selected output highway during the time slots identified as idle status for carrying signals on the selected input highway to the selected output highway; detecting illegal words carried to the output highway from the input highway for indicating an idle status time slot on both the selected input highway and the selected output highway, and for partially testing the continuity of the enabled signal carrying path; identifying the last said time slot; whereby an available time slot is selected within one frame.

Claim 11

In a method of selecting idle time slots in cyclically recurring frames on a selected one of a plurality of input highways and a selected one of a plurality of output highways in a network of highways in a telephone system in which idle time slots on only the input highways are encoded with an illegal word and in which lists in status memory means indicate the time slots which have an idle status on each one of the output highways, the steps of: successively identifying the idle status of time slots on the selected output highway from said list in the status memory means for the selected output highway independently of the lists for each other output highway; enabling means to provide a signal path between the selected input highway and the selected output highway during the time slots identified as idle status for carrying signals on the selected input highway to the selected output highway; detecting illegal words carried to the output highway from the input highway for indicating an idle status time slot on both the selected input highway and the selected output highway, and for partially testing the continuity of the enabled signal carrying path; identifying the last said time slot; whereby an available time slot is selected within one frame.

Claim 12

Pathfinding apparatus for selecting time slots in cyclically recurring frames for a signal path between two selected lines of a digital switching network, having status memory means for listing the busy or idle stAtus of each time slot on one of said selected lines and having means for encoding available idle time slots on only the other of said selected lines with a signal indicating the availability of the time slots, a control comprising: means responsive to the listing in said status memory means for identifying the busy or idle status of each time slot on said one line; means including switching means enabled to provide a signal path between said selected lines during each time slot identified as idle on said one line for carrying signals between the lines; and means detecting an encoded signal carried to said one line from said other for indicating a time slot available on both of said selected lines, and means to register the identity of the last said time slot for use by processing apparatus.

Claim 13

Pathfinding apparatus for selecting time slots in cyclically recurring frames for a signal path between two selected lines of a digital switching network, having status memory means for listing the busy or idle stAtus of each time slot on one of said selected lines and having means for encoding available idle time slots on only the other of said selected lines with a signal indicating the availability of the time slots, a control comprising: means responsive to the listing in said status memory means for identifying the busy or idle status of each time slot on said one line; means including switching means enabled to provide a signal path between said selected lines during each time slot identified as idle on said one line for carrying signals between the lines; and means detecting an encoded signal carried to said one line from said other for indicating a time slot available on both of said selected lines, and means to register the identity of the last said time slot for use by processing apparatus.

Claim 14

In a path finding apparatus for selecting idle time slots in cyclically recurring frames for call signals between input and output highways of a telephone system having means encoding idle time slots on only the input highway with an illegal word indicating idle time slots and having status memory means listing the busy or idle status of each time slot on the output highway, a control comprising: identification means connected to said status memory means responsive to the listing in said status memory means for successively identifying the busy or idle status of output highway time slots; interconnection means including switching means connected to said identification means, said switching means being enabled to provide a signal path for carrying signals between the input highway and the output highway during the time slots identified as idle by said identification means; detection means connected to said output highway for detecting illegal words carried to the output highway, via said signal path, from the input highway so as to indicate a common time slot available on both the input and output highway; and register means, connected to said detection means, to register the identity of the last said common time slot for use by a processor to establish a call connection.

Claim 15

In a path finding apparatus for selecting idle time slots in cyclically recurring frames for call signals between input and output highways of a telephone system having means encoding idle time slots on only the input highway with an illegal word indicating idle time slots and having status memory means listing the busy or idle status of each time slot on the output highway, a control comprising: identification means connected to said status memory means responsive to the listing in said status memory means for successively identifying the busy or idle status of output highway time slots; interconnection means including switching means connected to said identification means, said switching means being enabled to provide a signal path for carrying signals between the input highway and the output highway during the time slots identified as idle by said identification means; detection means connected to said output highway for detecting illegal words carried to the output highway, via said signal path, from the input highway so as to indicate a common time slot available on both the input and output highway; and register means, connected to said detection means, to register the identity of the last said common time slot for use by a processor to establish a call connection.

Claim 16

Apparatus as in claim 9 wherein said detection means additionally comprises means for partially testing the continuity of the signal path established by said interconnection means.

Claim 17

Apparatus as in claim 9 including additional input highways and additional output highways and further including means for selecting a single input and output highway pair for each call signal and wherein said detection means is independent for each output highway.

Claim 18

In a pathfinding apparatus for use with a time division multiplex switching network having input means coupled to an input highway, an output highway coupled to output means, having established calls between said input means and output means, a switching device between said input highway and said output highway, each established call having an assigned time slot in cyclically receiving frames during which said input means is actuated to place said established calls, in the form of digital signals on said input highway, said switching device is enabled to pass said digital signals from said input highway to said output highway, and said output means is actuated to receive said digital signals from said output highway; wherein the improvement comprises first means connected to said input means for causing said input means to encode idle time slots on said input highway with an illegal word and control means comprising status memory means for storing the busy or idle status for each time slot on said output highway, scanning means, connected to said status memory means, for scanning the time slots of a frame, including identification means effective during each time slot to read the busy or idle status from said status memory, path set up means connected to said scanning means responsive to an idle status to enable said swithcing device to pass digital signals from said input highway to said output highway, an illegaL word detector coupled to said output highway which responsive to an illegal word supplies a path found signal, and means responsive to said path found signal, connected to said illegal word detector to register the identity of the current time slot as being selected for use by a processor.

Claim 19

In a pathfinding apparatus for use with a time division multiplex switching network having input means coupled to an input highway, an output highway coupled to output means, having established calls between said input means and output means, a switching device between said input highway and said output highway, each established call having an assigned time slot in cyclically receiving frames during which said input means is actuated to place said established calls, in the form of digital signals on said input highway, said switching device is enabled to pass said digital signals from said input highway to said output highway, and said output means is actuated to receive said digital signals from said output highway; wherein the improvement comprises first means connected to said input means for causing said input means to encode idle time slots on said input highway with an illegal word and control means comprising status memory means for storing the busy or idle status for each time slot on said output highway, scanning means, connected to said status memory means, for scanning the time slots of a frame, including identification means effective during each time slot to read the busy or idle status from said status memory, path set up means connected to said scanning means responsive to an idle status to enable said swithcing device to pass digital signals from said input highway to said output highway, an illegaL word detector coupled to said output highway which responsive to an illegal word supplies a path found signal, and means responsive to said path found signal, connected to said illegal word detector to register the identity of the current time slot as being selected for use by a processor.

Claim 20

Pathfinding apparatus as set forth in claim 12, wherein there is at least one additional input means and input highway, at least one additional output highway and output means, at least one additional switching device coupling each of said additional input highways to each of said additional output highways; wherein each output highway has an individual said control means, each said control means further including a storage register in which is stored the identity of a selected input highway, and said path setup means includes first gate means to gate said identity of said selected input highway from said storage register to identify the switching device to be enabled.

Claim 21

Pathfinding apparatus as set forth in claim 13, wherein for each said output highway there is a switching control memory storing the identity of the input highway being used by the call for each busy time slot on the last said output highway, and further gate means enabled during busy time slots to supply the identity of the switching device to be enabled, said further gate means being inhibited when said first gate means is enabled.

Claim 22

Pathfinding apparatus as set forth in claim 14, wherein each said control means includes a register for storing the identity of the time slot from which said scanning it to start, and means to inhibit the said first gate means until the occurrence of the last said time slot.

Claim 23

Pathfinding apparatus for use with a switching network for calls having time division multiplexed digital signals, said switching network having a plurality of input highways, a plurality of output highways, a plurality of crosspoints coupling each input highway to each output highway, and wherein a path for a call is provided by enabling the crosspoint between one of said input highways and one of said output highways during a selected time slot of cyclically recurring frames, input means placing digital signals for said call on the input highway of said path during said selected time slot, and output means receiving said digital signals for said call from the output highway of said path during said selected time slot of each frame; a new call having a selected input highway and a selected output highway with a selected crosspoint coupling said selected input highway to said selected output highway; said pathfinding apparatus comprising means to encode with an illegal word each idle time slot on said selected input highway, and control means individual to each of said output highways; said control means comprising a status memory which stores the busy-idle status of each time slot for said selected output highway, a storage register which stores the identity of said selected input highway, scanning means connected to said status memory to read said memory during each time slot, means connected to said storage register operative responsive to an idle indication from said status memory to use the identity stored in said storage register to enable said selected crosspoint for the current time slot, an illegal word detector coupled to said output highway to detect said illegal word, and means responsive to detection of said illegal word to register the identity of the current time slot as being selected for said new call for use by a processor.

Claim 24

Pathfinding apparatus for use with a switching network for calls having time division multiplexed digital signals, said switching network having a plurality of input highways, a plurality of output highways, a plurality of crosspoints coupling each input highway to each output highway, and wherein a path for a call is provided by enabling the crosspoint between one of said input highways and one of said output highways during a selected time slot of cyclically recurring frames, input means placing digital signals for said call on the input highway of said path during said selected time slot, and output means receiving said digital signals for said call from the output highway of said path during said selected time slot of each frame; a new call having a selected input highway and a selected output highway with a selected crosspoint coupling said selected input highway to said selected output highway; said pathfinding apparatus comprising means to encode with an illegal word each idle time slot on said selected input highway, and control means individual to each of said output highways; said control means comprising a status memory which stores the busy-idle status of each time slot for said selected output highway, a storage register which stores the identity of said selected input highway, scanning means connected to said status memory to read said memory during each time slot, means connected to said storage register operative responsive to an idle indication from said status memory to use the identity stored in said storage register to enable said selected crosspoint for the current time slot, an illegal word detector coupled to said output highway to detect said illegal word, and means responsive to detection of said illegal word to register the identity of the current time slot as being selected for said new call for use by a processor.