| 摘要 |
A common porch entrance control system having an automatic transfer device is provided to reduce costs significantly by performing output through one video phone terminal of each household of an apartment house. A common porch entrance control system comprises a lobby door phone(200), a door phone(100), a display device, and an automatic videophone switch(400). The lobby door phone is installed in a common porch. A household door phone is connected to a videophone system in response to a received visit request signal. An audio signal inputted from the door phone or the lobby door phone is received and outputted. The display device outputs a video signal, inputted from the door phone, through a video signal buffer part. The automatic videophone switch outputs the video signal, inputted from the door phone, through a differential twist receiver to the display device of the video phone system.
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