GB1466433A - Data insertion device - Google Patents

Abstract

1466433 Automatic exchange systems INTERNATIONAL STANDARD ELECTRIC CORP 12 Sept 1974 [18 Sept 1973] 39790/74 Heading H4K Signalling or control information can be switched through a speech store of a TDM exchange either by using storage locations associated with free speech channels or, if all speech channels are in use, by utilizing the storage location of a busy speech channel. In the latter case the speech information which would have been switched is cancelled, the arrangement being subject to the constraint that only a predetermined amount of speech information associated with a particular channel may be cancelled. In normal operation speech samples are fed from a register 24 into locations of speech store 1 under the control of addresses which respectively appear in register 22 half a time slot earlier, and a connection store 2 controls the read out for the speech store locations. During the half time slots during which samples are being read into store 1, a central control can insert a binary 1 into any storage position of a further store 16 to indicate that it wishes to utilize the corresponding location of store 1 for transferring signalling or control data. When the particular storage location is due to be written into as indicated by the appearance of the location address in register 22, the binary 1 signal in store 16 is fed to register 19 to prevent any speech information in register 24 from being written into store 1 during the following half time slot. As a result the data from central control 11 is written into the store 1 for subsequent read out as determined by information fed into connection store 2 by the central control. The central data may relate to maintenance messages for testing the speech network, a message inserted into the speech store 1 being compared with the original message after it has been switched through the network.