Time division self-correcting switching system

Claim 2

A line concentrator for connecting a plurality of subscriber lines to a central office through a lesser number of links characterized by: a. means for generating signals at a frequency representing a base cycle for scanning all of said lines; b. means for generating a second-order cycle whose frequency is a submultiple of said base frequency for scanning said links; c. a subscriber unit connected to said plurality of subscriber lines; d. an exchange unit connected to said central office; and e. means included in each of said units being responsive to said base cycle means for establishing a connection between said subscriber unit and said exchange unit through said links.

Claim 3

A line concentrator according to claim 1 including means for the continuous supervision of different operation conditions, means for the automatic correction of wrong connections, and means for generating a cyclical repetition of control instructions, said cyclical repetition means including means for discriminating between instructions and noise.

Claim 4

A line concentrator according to claim 1 characterized in that the subscriber unit includes a cross-point matrix for connecting the subscriber lines to the links and the exchange unit includes a cross-point matrix for connecting the links to the central office, said matrices being symmetrical and controlled by logic control circuit means, said logic control circuit means including corresponding circuits in the subscriber and exchange units and exchanging control and synchronization data through a single auxiliary transmission link.

Claim 5

A line concentrator according to claim 3 characterized in that said logic control circuit means comprise, a. a step ring counter counting steps in the base cycle, said counter allotting a time slot in said base cycle for each of a plurality of operations, such operations including the connection of a subscriber to a link, the disconnection of a link, and the synchronization between the subscriber and exchange units; b. a cycle ring counter for counting base cycles of said step counter and distinguishing them alternately in scanning cycles and distribution cycles; c. a. second-order ring counter counting cycles of said cycle counter and allotting each couple of said base cycles to a link; and d. means for synchronizing the steps of each of said ring counters whereby the step counter and the second-order counter in the subscriber unit are in phase with the corresponding counters in the exchange unit while the cycle counter in the subscriber unit is in phase opposition to the cycle counter in the exchange unit.

Claim 6

A line concentrator according to claim 4 characterized in that said subscriber and exchange unit comprise a scanner distributor circuit for detecting and distributing call signals, the operation of said scanner-distributor circuit being controlled by the step counter, the cycle counter and the second order counter in such a way that the step counter defines the subscriber to be connected, the second-order counter defines the link to be connected, the cycle counter defines whether the scanner distributor circuit is operating as a scanner or as a distributor, said scanner distributor circuit including means for detecting, during its operation as a scanner, call signals corresponding to the subscribers singled out successively by said step ring counter and including means for activating in the cross-point matrix the row control circuit corresponding to said subscribers if a call signal is detected, said scanner distributor circuit including means for activating during its operation as a distributor the row control circuit in the cross-point matrix corresponding to the subscribers singled out successively by said step ring counter if the receiver on the auxiliary transmission link detects a call signal from the other unit, said line concentrator further including means responsive to call signals activating the row control circuits for activating with the same signals the column control circuits in the cross-point matrices corresponding to the links singled out by the second-order ring counters, said line concentrator further including means responsive for sending said call signals over said auxiliary transmission link.

Claim 7

A line concentrator according to claim 5 characterized in that every said column control circuit comprises a column relays holding circuit; said holding circuit including means for hindering when activated further call signals through said column control circuit.

Claim 8

A line concentrator according to claim 6 characterized in that the availability state of each link in the exchange and subscriber units is stored during the corresponding second order cycle in a storage element activating said scanner distributor circuit to send a possible call signal; said storage element being set to a nonavailability state by a signal corresponding to the initiation of each second order cycle said nonavailability state of the storage element remaining until a control signal, generated under control of the step ring counter, enters said column control circuit whereby, if said column relays holding circuit is not activated, a signal of availability will be developed which is transmitted to the input of said storage element to change its state.

Claim 9

A line concentrator according to claim 7 including in said exchange unit a link supervision and release circuit controlled by said step ring counter and said second order ring counter responsive to the real state of the busy links; said link supervision and release circuit sending a release signal in a time slot defined by the step ring counter if the link singled out at that time by the second order ring counter has been released, said generated release signals arriving at a guard circuit included in the link supervision and release circuit, said guard circuit sending a release instruction to the column relays holding circuit after a count of a fixed number of release signals associated to the same link has been received, said line concentrator further including means for sending said release instruction to the subscriber unit.

Claim 10

A line concentrator according to claim 8 characterized by a reference circuit included in said link and supervision release circuit, said reference circuit including means for receiving at a first input signals coming from a subscriber unit and indicating the availability state of said links in said matrix and at a second input signals coming from the local link control circuit indicating the link availability state in the corresponding matrix, said reference circuit comparing said signals and if there is a difference sending a release signal to the guard circuit.