Circuit arrangement for videotex operation in telephone branch exchanges, particularly key-type and executive-secretary systems

摘要

If it is intended to equip a telephone exchange for videotex operation, only one separate videotex decoder is in each case allocated to the individual telephone sensors which are involved. At the telephone branch exchange, only the same number of devices required for the videotex operation, for example subscriber line unit, videotex modem, as the number of videotex connections to be simultaneously set up is connected. From a videotex decoder directly interconnected with in each case one videotex modem, an audio frequency signal is generated with the aid of a special interface circuit, which signal is connected, via the switching network of the telephone branch exchange, through to the telephone terminal carrying out the videotex connection. If the videotex modem is allocated to a telephone terminal, the associated videotex decoder is responsible both for the relevant telephone terminal and for interaction with the videotex modem.