| 摘要 |
940,191. Telegraphy. STANDARD TELEPHONES & CABLES Ltd. Sept. 8, 1961 [Sept. 12, 1960], No. 32371/61. Drawings to Specification. Heading H4P. In a telegraph switching centre comprising one or more incoming lines and a number of outgoing lines, each line has associated with it a store and a transmitting means, and also means for transmitting on an established crossoffice connection a parity check signal with each character code combination. This parity signal is compared at the outgoing line store with a derived parity signal. In the embodiment described incoming signals are in 5-unit code and each message includes routing signals and " start of message " and " end of message" signals. Associated with each line is a tape perforator and tape transmitter. After the incoming signals are stored at the receiving units a director sets up cross-office connections between the incoming stores and the outgoing stores at the sending units that serve the addresses specified by the routing signals. If the sending units requested are idle an allotter operates to ensure that only one cross-office connection is made at any time, and also prevents more than one receiving unit from being connected to the same sending position at any time. A parity bit is derived at the receiver unit and is transmitted crossoffice with the message signals. This parity bit is stored and as the tape store at the sending unit is read out a corresponding parity bit is derived and compared with that transmitted. If a message has a multiple address, i.e. is to be transmitted over more than one outgoing line, it is routed to a multiple address unit and when the paths from the incoming tape reader to the outgoing tape perforators are set up the message is transmitted over all these paths simultaneously. However, if a parity check at any outgoing tape reader indicates an error, the signals on that tape are not sent to line. Signals from the other tapes are not inhibited. In the event that a multiple address message is passed through several switching centres, a switching centre ignores the routing signals indicating addresses served by a centre through which the message has already passed. |
