| 摘要 |
PURPOSE:To reduce the cost of a system and to improve the operability by providing an operation detecting means detecting the operation of a telephone set to operate an external device, a switching means switching a display signal of an external device and a power application means. CONSTITUTION:The operation detection means 1 detects the operation of a handset (off hook) of a called party when a telephone call comes to a television telephone set or detects the operation of a television telephone set by the caller. The result of detection is fed to a switching means 2, a power application means 3, and when a video signal A from an external device such as a television set is fed to the means 2, the means 2 selects a video signal B of a television telephone set or the like to give an output to the display means of the external device. Since the external device uses the operating start signal of the means 1 and the means 3 starts the operation of the external device, then even if the external device is not in operation, the external device is operated automatically and the video signal of a television telephone set or the like is displayed. Thus, the inexpensive system is attained and the operability is improved.
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