GB1290278A - - Google Patents

Abstract

1290278 Automatic exchange equipment INTERNATIONAL STANDARD ELECTRIC CORP 19 April 1971 [23 April 1970] 27265/71 Heading H4K In a telecommunication system data is transmitted as frequency modulated signals in one frequency band for transmission within an exchange and in a second frequency band for inter-exchange working and the frequency conversion occurs in an exchange modem which is seized for the inter-exchange connection. Both a data set FSM and a normal telephone set are connected through a modem T-Mo, line Ltg to the exchange switch TKF. For a connection within the exchange, i.e. intra-exchange traffic, a connection set JVS is assigned and the connection established over a further switch JKF. A changeover switch in the modems is now operated to interconnect the data sets through the modulating and demodulating circuits tuned to the intra-exchange frequency band. It is stated to be possible to cause the second data set to respond when unattended either by dialling an additional code or by operating the changeover switch in T-Mol which causes a pilot tone to be transmitted. For an inter-exchange call the connection from the switch TKF is taken through switch RKF and exchange link AVS to trunk A-Ltg. If data is to be transmitted over this connection a centrally disposed modem A-Mo is seized for adapting the intra-exchange signals to interexchange signals. Rerouting through modem A-Mo is obtained by use of a key at the substation or as a result of the operation of the changeover switch in the subscribers modem.