| 摘要 |
PURPOSE:To avoide the impossibility of data transmission due to runaway of some transmission control circuit by resetting transmission control circuits consisting of CPUs if a transmission signal cannot be obtained over a certain time. CONSTITUTION:When the address of an optional divelling unit 3 is inputted in an entrance unit 1 or a janitor room unit 2, call control data which calls individual develling units 3 is transmitted through signal lines 4a and 4b, and the pertinent unit is called, and its interphone transmitter and receiver is connected to a service line 4b to make the service possible. If a transmission control circuit 11 of th entrance unit 1 runs away and is reset internally, the janitor room unit 2 continues to wait for data transmission, but a reset pulse is outputted from a counter 23b of a reset circuit 23 after a prescribed time because a busy signal is not outputted from a busy detecting circuit 22, and data transmission is restarted. |
