| 摘要 |
<p>To provide a network control unit which does not necessitate in crease in size, in the number of component parts and in the manufacturing cost, a network control unit 1 connected between a telephone switch board 5 and a communication terminal device 6 is constructed by a circuit line transformer 4 for superimposing an alternating current component indicative of a voice signal of the communication terminal device on a circuit line current from the telephone switchboard 5 and for extracting the alternating current component superimposed on the circuit line current to produce the extracted component to the communication terminal device, a DP transmitting circuit 2 for transmitting a dial pulse signal to the telephone switchboard 5, and a direct current loop circuit provided in the DP transmitting circuit 2 for forming a direct current loop from La to Lb through D1, d1, d3, PH3, Q1, R5, d4, d2 and D2 thereby to enable communication between the telephone switchboard 5 and the communication terminal device 6. <IMAGE></p> |
