Data transmission over automatic telephone system - has two modems each with time element started simultaneously with MODEM switching

摘要

The transmission is intended for a manned calling station and a manned or unmanned called station. When the called station subscriber line is switched over from its telephone instrument to the corresponding modem, it automatically sends a reply tone which switches over to the respective modem the line at the calling station. At this signal end signalling wires "readiness for operation" of both stations are switched to "ON" state. A timer is provided in each modem, started when the line is switched over. At the end of the delay time, and in case of distorted reply tone at the calling station, the modem is made ready for operation, or the line is switched over from the modem to the telephone instrument.