Isolating interface between a telephone line and a digital circuit

摘要

The digital input and output of the modem are formed by the input-output interfaces of converters (DIG-PART). A voltage isolating barrier (20') is inserted between the digital parts (50) and the analogue parts (51) of the converters. The digital parts of the converters are connected to the user equipment side of the modem, and the analogue parts are connected to the telephone line. The converter (11) (2W/4W) consists of an analogue signal duplexer which is connected to the line. The analogue heads (51) of the converters and the circuit (11) are supplied with a continuous voltage from the telephone line (generally -48 volts).