Patent GB-1123460-A (GB)
Title: Automatic telecommunication switching system
IPC: H04Q3/54
Filed: 1966-10-07
Abstract: 1,123,460. Telephone exchange systems. INTERNATIONAL STANDARD ELECTRIC CORP. 7 Oct., 1966 [8 Oct., 1965], No. 44838/66. Heading H4K. In a switching system wherein a calling line LC1-1000, Fig. 1, is connected by a control arrangement M to a free register of a group LR1-20 through switches TSS1, PSS1 having a plurality of outputs 1-12, and switching means, which may comprise a local connecting circuit LCC, and a register-finder RF1, RF2, and wherein the information received by the register is passed by a connecting circuit to the common control arrangement whereby the effective output of the plurality is connected back through the switches to the wanted subscriber, the common control arrangement comprises a pair of circuits PCC, SCC, one controlling the connection of a calling input to one of the said outputs and the other the connection of the one output to the wanted subscriber, which are able to perform at least part of their operations simultaneously. The two circuits each have passive and active phases i.e. a selecting or setting up phase, and a switch operating phase, and include inhibiting circuits whereby simultaneous active phase operation is prevented. In a PBX using cross-bar switches TSS1, PSS1, two-position select bars prepare the connection of an individual switch connected to an output, to a pair of inlets, a supplementary bar selecting the one of the pair to be connected. Each terminal section cross-bar has two links to each primary section cross-bar providing access to 54 local connecting circuits LCC. A terminal section calling condition operates relays (TAR) (PAR) if electromagnet auxiliary contacts reveal that a free link exists, four relays (TAR) being provided together with lock-out circuitry. The actuated (TAR) relay prepares the operation of the corresponding horizontal electromagnet, and selection of one from a number of simultaneously operated (PAR) relays is controlled by a priority distributer and lock-out circuit, a relay (PCR) indicating in the PCC that selection has been made. Relays (PBR) (PCR) establish a control circuit through contacts associated with the vertical bar electromagnets in the two stages if the bars are free, and the establishment of a connection between a selected terminal section TS 1 and at least one local connecting circuit LCC through at least one primary section PS is indicated by operation of corresponding relays (1PDR)-(9PDR), relays (PER) (PFR), in the PCC indicating that a selection of the available primary section has been made by a lock-out circuit (SC2). Relay (AR1) in the selected primary section initiates connection of the primary section to a free register in a manner not described, but in which the free condition is indicated by a relay (EPR), and a relay (PXR) is operated when all are engaged. If SCC is inactive the prepared horizontal bars in both stages are actuated and their actuation in TS1 and PS1 respectively is indicated in PCC by relays (PJR), (PKR), responding to auxiliary contacts on the electromagnets. The connection of a free register to the local connecting circuit involved is not described but a relay (PLR) in PCC indicates the connection and the vertical bars are successively operated, to complete the first step in the connection, i.e. calling line to register. A cross-bar switch "X" contact releases the operated relays of PS1, TS1, and a relay (PNR) of PCC operates to indicate completion of preselection. All the relays are released and PCC is disconnected from the register. A relay (PHR), in releasing, makes PCC available for the next call and permits the operation of a relay (SER) to allow an active phase of SCC. Relay (EDR) operated on completion of digit registration inserts the winding of a relay (ECR) into a distributer and lock-out circuit, and one filled register is selected by SCC, and three coded digits therefrom are transferred to a store (1SC) comprising groups of relays, in SCC. The store relay contacts provide a path to the horizontal electromagnets for effecting connection between the terminal section and the called subscriber, and to those corresponding to the second PSS output to the LCC in use, for linking the PSS to the TSS including the called subscriber. Actuation of the horizontal bars is indicated by a relay (SJR), and if the called subscriber is found to be free, electromagnet (FSR) actuates the vertical bar in PSS1 associated with the second output to the local connecting circuit LCC used in preselection, to connect the speech path back to the terminal stage where the second vertical bar is actuated to complete the connection. The register and the relays in SCC are released and PCC is unblocked. Application of the invention to a 3000 line system using three switching stages and three markers is described in conjunction with Figs. 8-12 (not shown), and in this embodiment operation of a single cross-bar by two control circuits is prevented. Multi switches may alternatively be used.