| 摘要 |
PURPOSE:Not to compulsorily disconnect the call of a doorphone even when a guest comes to a lobby by switching a speaking circuit from the doorphone to a lobby interphone with the AND between a call signal from the lobby interphone and a hook switch ON signal. CONSTITUTION:When the call signal is inputted from a lobby call terminal 5 in a control circuit 6, the circuit 6 outputs the signal to a ringing tone generation circuit 9 and makes a speaker 11 ring through an amplifier 10. Only when both the call signal and the hook switch signal from a hook switch signal detection circuit 8 are ON, namely with the AND of both signals, the circuit 6 outputs the signal to a relay driving circuit 12 so as to switch the speaking circuit and switches the connection to an interphone circuit 4 from a doorphone call terminal 2 to a lobby call terminal 1. Thus, in case of executing the call with the doorphone a caller listens to the ringing tone and hooks on a telephone receiver once. And when the hook switch is ON, the call is switched.
|
