Serial data transmission by supply volage pulse modulation - enables terminal to receive and transmit simultaneously by interruption of current on line via exchange receiver

摘要

Each interface (5) at a central exchange linked by a two-wire line (12, 13) to a terminal (11) incorporates a data transmitter (15) including a controllable voltage regulator (LM) and a transmission key transistor switch (T1) earthing a feedback voltage divider (R2, R3). Data are transmitted from the exchange by voltage redn. and from the terminal transmitter (17) by current interruption (T3), while supply is maintained by a storage capacitor (C3) or buffer battery. The exchange receiver (14) includes a transistor switch (T2) and amplifier (T5). USE/ADVANTAGE - Esp. in telephone system, data transmission capacity over power supply lines exceeds that of half-duplex operation.