PURPOSE: To set optionally a subscriber circuit to be broadcasted and to modify easily the range of a broadcasting output by providing a control circuit switched for inputting a broadcast sound to a telephone set at every subscriber circuit, and controlling the control circuit by a microcomputer.
CONSTITUTION: A subscriber 1 has a hook switch 12 and a speaker 13 for outputting a broadcast sound. Terminals 14 and 15 of a subscriber circuit 4 are those for inputting a control signal from a central control part 9. When a control signal is inputted from the terminal 14, a photocoupler 22 is activated, and a CO relay becomes the closed condition and separated from a line. An L relay 24 is that for detecting hook on/off and detects the case of terminals 29 and 30 are short-circuited and transmits the detected result to the central control part 9. When a broadcast sound is outputted to the subscriber 1, a signal is transmitted to the terminal 15 from the central control part 9, a photocoupler 23 is activated and a BR relay operates. Thus the broadcast sound is put on the air from terminals 36 and 37. In order to detect the hook on/off of a telephone set during broadcast, the same DC bias as that of terminals 27 and 28 are applied to the terminals 36 and 37.
Next Patent: WIRE BROADCASTING TELEPHONE EXCHANGE