| 摘要 |
PROBLEM TO BE SOLVED: To prevent lightning surge preventing connectors provided between a main line connecting an entrance slave transceiver to a master transceiver and an AC power source, from being left in unconnected states. SOLUTION: A television doorphone device displays the picture of a visitor photographed by the entrance slave transceiver 1 with camera on the monitor 7 of the master transceiver 2 with monitor through the main line 25 when the visitor depresses the button of the slave transceiver 1. The main line 25 is connected to the AC power source 18 through the lightning surge preventing connectors 21a and 21b which are connected after a withstand voltage testing step is performed on the television doorphone device and a lightning surge absorbing element arrester 19. The doorphone device is provided with a voltage detecting terminal 22 which detects the voltage of the main line 25 between the lightning surge preventing connectors 21a and 21b and lightning surge absorbing element arrestor 19, for confirming that the connectors 21a and 21b are connected at the time of avoiding the unconnected states of the connectors 21a and 21b after the withstand voltage testing step is completed. COPYRIGHT: (C)2005,JPO&NCIPI
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