| 摘要 |
PURPOSE:To avoid the simultaneous calling given from plural terminal stations, by transmitting repetitively an inpulse of a certain time length onto a cable circuit from a main terminal station to control the slave station. CONSTITUTION:The adverse logic of an output that passed through a low pass fiter BR of a receiving circuit is obtained through an inverter I. Then an AND of the above-mentioned logic and a counter circuit MX is obtained through an AND circuit AND1. Thus an output pulse is obtained when the DC output voltage on a cable is off. When a terminal station has the contents of communication, as a flip-flop F2 is being turned on, a pulse showing that the circuit is idle turns on a flip-flop F3 through the circuit AND2, then, a busy signal is applied to the circuit through a low pass filter BS of the receiving circuit. |
