| 摘要 |
A hook flash actuated telephone control device that is connected into a subscriber's telephone line to permit a user to place an existing call on hold by selectively activating the hook switch of his telephone according to a particular sequence. The control device includes a comparator which senses the line voltage and produces an output signal, the level of which is dependent upon whether or not the telephone handset is in an on-hook or off-hook condition. First timing and logic means are interconnected so as to be triggered by the output signal of the comparator. If the telephone handset is in an off-hook condition and the hook switch flash signal sequence is completed within a first particular predetermined time, a corresponding signal is generated to energize a hold circuit, whereby to place the telephone circuits in a hold condition. Audio signal generating means are also energized in order to provide the user with a tone to indicate that the telephone circuits are rendered in a hold condition. Accordingly, the user may return the handset to the telephone cradle without disconnecting the existing caller. Second timing and logic means are also provided to automatically reset the user's telephone circuits to receive new incoming calls, should the user inadvertently place his telephone circuits in a hold condition for longer than a second predetermined time. To resume an existing telephone call, the user merely raises the handset from the cradle of his telephone or any extension thereof, whereby the line voltage changes and the hold circuit is subsequently de-energized.
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