| 摘要 |
<p>PURPOSE:To realize a mutual call signal system of the same structure as the calling talk with the general subscribers by installing a means to break the DC loop circuit of the calling subscriber to the reverting call trunk as well as the party line telephone and then transmitting the calling signals to the called subscriber. CONSTITUTION:For the reverting subscriber mutual calling, common telephone 1 and reverting B-telephone 2 of the reverting subscribers are connected to reverting A-telephone added circuit 3 and reverting B-telephone added circuit 4 respectively. Then telephone 1 and 2 are connected to reverting call trunk 5. Switching relay contact rv is provided to trunk 5 to perform the individual calling, and the contact operates for the outgoing of the B-subscriber and does not in the case of the A- subscriber outgoing. Furthermore, relay contact S is provided to transmit the outgoing cut-off signals to the calling subscribers. Contact S operates when the connection is completed with the calling subscribers to cut off the DC loop circuit of the calling subscribers.</p> |
