| 摘要 |
PURPOSE:To prevent a crosstalk from generating, and to improve the quality of a call, coping with a request to extend a channel length according to a tendency to make a multiple dwelling house into a large-size, by providing an unbalancing-balancing conversion circuit in the door phone channel of a call device provided at each dwelling unit. CONSTITUTION:A building manager office master machine 13, a multiple hallway machine 14 arranged at the common hallway of a multiple dwelling house, and a call device l5 arranged within each dwelling unit, are connected by a channel l7 through an adapter 16, then constituting a system. The adpater 16 has a function to control the call from the master machine 13 and the hallway machine 14, to each call device 15, and alarms for various kinds of sensors, such as fire or gas leak within the dwelling unit. And the call device 15 has a door phone channel 18 using a PE insulated PVC sheath twin type city cable(with aluminium tape shielding for static electricity shield) in which two cores are cabled uniformly. Also another power source is provided in a call circuit between the master machine 13 and the hallway machine 14. An unbalancing-balancing conversion circuit 10 consists of an insulating transformer, and it is provided in the door phone channel of the call device l5 in the adapter 16, and performs the call with the master machine 13 or the multiple hallway machine 14.
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