| 摘要 |
PROBLEM TO BE SOLVED: To provide a multiple dwelling house interphone system that suppresses a current consumed at a call from a visitor at a central entrance or a house entrance and at unlocking an electric lock on the entrance door of the central entrance so as to save the power and ensures excellent speech quality suppressing howling. SOLUTION: In the multiple dwelling house interphone system, at least one central entrance unit 1 comprising; a speech module 10 for making a call/speech; and a call switch for channel selection and calling connected to the speech module, a bus controller 4 that supplies power to the common bus and a plurality of living room master units 2, 2, etc., for calling/making a speech with the central entrance unit are connected to a common bus 3 in parallel, the bus controller is provided with an impedance increase circuit 51 to increase the output impedance, and a speech module of the central entrance unit and each living room master unit are respectively provided with resistors R4, R13 connected to the common bus. |
