| 摘要 |
<p>The testing system, for testing shared-service telephone lines neither of which are directly connected to the exchange's selection circuits, has a test console passing control signals and detecting 'loop-closed' signals and 'listening' signals when one or the other or both the subscriber terminals are engaged. The test console also detects when the power supply has failed. The line circuits connecting the exchange to the shared line and the subscribers to the shared line each have an intermediate line to which bistable relays can connect as required the voice lines of either the one or the other voice circuit. Further bistable relays connect the intermediate lines to both ends of the shared line depending on whether both subscribers are engaged or free..</p> |
