| 摘要 |
PURPOSE:To allow a user to perform channel selection easily and to simplify the constitution of a device, by providing channel selection control circuits, for selecting control over a preferential and a nonpreferential subordinate device, and a call timer holding circuit which holds a call from the nonpreferential subordinate device for a prescribed time and controls the channel selection control circuits. CONSTITUTION:To channel selection switch circuits 1 and 2 of a master deviceI, a subordinate device II, preferential subordinate device DI, and nonpreferential subordinate device DII are connected respecitvely. To those circuits 1 and 2, a priority channel selection control circuit 3 and a channel selection control circuit 4 are connected respectively. Then, the timer holding circuit 5 holds a call from the nonpreferential subordinate device DII for a prescribed time by its call signal. By a trigger signal sent from a call signal control circuit 9 within a prescribed time, the control circuit 4 is brought under the control of the holding circuit 5 to turn on the circuit 2. This constitution facilitates user's channel selection operation to simplify the constitution of an interphone device. |
