| 摘要 |
PURPOSE:To eliminate the need for the provision of a simultaneous start preventing circuit for an exchange at the called party, by connecting a strap to a caller when a power supply is interrupted and earthing the circuit, disconnecting the strap from the called party, and making the circuit open. CONSTITUTION:Relays 71-724 give outputs to an SR line of channels 1-24, i.e., channels CH1SR-CH24SR and they are constituted with transistors. Since a switch SW3 is set off when the power supply is applied normally, diodes D1- D24 are reverse-biased and the relays 71-724 are operated independently at each channel. Further, when the power supply is interrupted, the SW3 is set on, the diodes D1-D24 are forward-biased at the same time and each SR line of the channels CH1-CH24 is earthed. Since the SR line connected to the called party disconnects all straps 10i at a central controller when the power supply is interrupted, each SR line of the channels CH1-CH24 is opened, then no simultaneous start happens. |
