| 摘要 |
PURPOSE:To prevent the generation of crosstalk among plural slave devices and to attain the simultaneous call in both directions to improve the operability of an interphone system, by providing the oscillation circuits of the 1st and 2nd carrier frequencies different each other to plural communication devices. CONSTITUTION:The 1st slave device 1 is connected to a master device 2 serving as a communication device via an exclusive line 3, and the device 1 contains a microphone 4 and a speaker 5. At the same time, the device 2 is connected to a power line 7 connected to a commercial AC power supply 6 and then energized by the power supply 6. In addition, the 2nd slave device 8 serving as a communication device is connected to the power supply 6 via the line 7 and energized by the power supply 6. Then handsets 9 and 14 containing microphones 10 and 15 and speakers 11 and 16, the chennel selection call push-buttons 12 and 17 and pilot lamps 13 and 18 are provided to the devices 2 and 8 respectively. Then the oscillating circuits of the 1st and 2nd carrier frequencies different each other are provided to the devices 2 and 8 respectively, and the sounds modulated by these different carrier frequencies are superposed via the line 7. Then the modulated wave given through the line 7 is demodulated with the other modulated wave. In such a way, the crosstalk is prevented among slave devices. |
