| 摘要 |
PURPOSE:To recognize from which room a call comes by a display device by providing a call detection means connecting a main body device and a transmitter arranged to each room by 2-wire and detecting the operation of a transmission button short-circuiting the two wires, a display device and a buzzer. CONSTITUTION:When the transmission button 8 of the transmitter 2 is depressed, the wires connecting a main body device 1 and the transmitter 2 are short- circuited and a current flowing to a resistor R1 of the transmission detection section is increased, then a voltage across the resistor R1 is increased and transistors (Trs) Q4, Q3 are turned on. In this case, an output inverted via an inverter 1 goes to a low level, then a display light 3 of a display section 16 corresponding to the depressed transmission button 6 is lighted. In the notice sound generating section 18, a TR Q6 is conductive in the presence of a call from any transmitter 2, an output of a basic oscillation circuit 19 is applied to a buzzer 6 to cause a buzzer tone from the buzzer 5. Thus, depressing the transmitter button 6, a person of a room having the main body device 1 is called and the person in the transmitter side 2 is called by using reply call buttons 211-214 of the main body device 1.
|
