| 摘要 |
A telephone ring signal detector is coupled to a telecommunication line for detecting a first telephone ring signal, and for discriminating the first telephone ring signal from other line signals on the line. This detector comprises an event generator, coupled to the line, for receiving an incoming signal and for generating an initial event signal and an ending event signal, and a signal characteristic generator, coupled to the line and to the event generator, for generating a signal characteristic of the incoming signal after the initial event signal. This detector further comprises a signal characteristic limit device, for generating a predetermined signal characteristic range limit of the first telephone ring signal, and a signal characteristic comparator coupled to the signal characteristic generator, to the signal characteristic limit device and to the event generator, for comparing the signal characteristic with the predetermined signal characteristic range limit. A valid compare signal is generated when the signal characteristic is within the predetermined signal characteristic range limit. A ring detect signal is generated during the first quarter cycle time period of the first telephone ring signal in response to the valid compare signal and the ending event signal having occurred. The detector further comprises a line impedance device coupled to the signal characteristic comparator and to the line for activating an off-hook condition on the line during the first quarter cycle time period of the first telephone ring signal, in response to the ring detect signal.
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