To provide an interphone device which uses a port of a CPU circuit and executes control, monitor or the like of a DC voltage of a line.
The interphone device calls an interphone master 3 and an interphone extension master 5 from a porch slave 1 through a line L2; and makes a telephone call by a telephone call unit 13 of the porch slave, a telephone call unit 36 of the interphone master, and a telephone call unit 55 of the interphone extension master. The interphone master and the interphone extension master comprise voltage detection/voltage hoisting CPU circuits 39, 57, respectively, in which the interphone master or the interphone extension master detects and monitors the DC voltage of the line for connecting the interphone master and the interphone extension master, respectively, and controls the DC voltage of the line mutually, thereby grasping each state or request.
| JP4161094 | Apartment house intercom system |
ISHII MASAHIRO
TSUNEKAWA HIROYUKI
Hiromichi Watanabe