| 摘要 |
PURPOSE:To realize the miniaturization of the trunk circuit by connecting the current direction detecting circuit in parallel to the impedance to connected to the DC current path of the trunk circuit of the telephone circuit and then carrying out the signal transmission and reception among the automatic exchanges while the detection output of the current direction detecting circuit exists. CONSTITUTION:Coil RPTA is connected in series between call lines LA and LB to the trunk circuit which receives the signals among the exchanges via the direct current flowing to lines LA and LB which connect the two automatic telephone exhanges. In addition, comparator IC2 to detect the direction of the current flowing to lines LA and LB plus the current direction detecting circuit consisting of diodes D6 and D7 are installed in parallel to coil RPTA. And in case the current featuring the same direction as that to the 2nd input terminal from the 1st input terminal of the above detecting circuit exists at lines LA and LB each, the current direction is detected. And the prescribed output is applied to control circuit CONT via lead (2) to actuate relays A0-A1 plus OG. Thus the control is given to contacts a0 and a1 of the trunk circuit plus contact Og as well. |
