| 摘要 |
PURPOSE:To attain the transmission and reception of interphone signals and to selectively use the interphone, when a transmission signal from a main operation control panel is stopped. CONSTITUTION:When an output is given from an interphone connection control circuit 9 with an interphone operation input, the 1st connection circuit is operated via an input inhibition circuit 10 and the 1st time constant circuit 11 to connect a low frequency signal short-circuit 8 to a signal line 2. The transmission signals on the signal line 2 is lowered and the main operation control panel stops the transmission signal. The output of the circuit 10 activates the 2nd connection circuit 15 via the 2nd time constant circuit 13 and an OR circuit 14 and connects an interphone circuit 16, a connection request signal generating circuit 17, and a cut-off request signal generating circuit 18 to the signal line 2. The circuit 17 transmits the connection request signal of the address set at the 1st address set circuit 19 to the signal line 2. The interphone at the reception side receives the connection request signal with a connection request signal detection circuit 20 of the address set at the 2nd address set circuit 21 to attain the transmission and reception of interphone signals. |
