DIGITAL DATA TRANSMISSION LINE INTERFACE FOR TELEMETERING SYSTEM

摘要

The supervisor and the terminals are isolated using photo couplers to prevent damages caused by the surge voltage coming through the telephone lines. The data transmission between the supervisor and teh terminals is performed using two telephone lines. The circuit includes a first photocoupler (PC1) drived by the output siganl of the transmission port of the supervisor to modulate the transmitting data to have a first power level and for transmitting through a first connection node, a third photo coupler (PC3) drived when the first power level data are transmitted through the communication lines (T/RL) for applying the data to the receive port of the terminal, a fourth photocoupler (PC4) for modulating the transmission data of the terminal to have the second power level for transmitting to a second connection rode, and a second photocoupler (PC2) for transmitting the second power level data to the receive port of the supervisor.