| 摘要 |
<p>A telephone ring detector (10) detects a ring signal voltage (60) from a diverse set of signals transmitted on a telephone line (12) before a complete alternating current ring signal cycle (58) is received. In an exemplary embodiment, the ring detector (10) includes a voltage threshold setting device (32) for establishing a voltage threshold (62) and comparing the ring signal voltage (60) to the voltage threshold (62) to provide an output signal (64) when the ring signal voltage (60) is above the voltage threshold (62). A pair of zener diodes (46, 48) having a selected voltage value can provide the threshold setting and comparison functions. A microprocessor (34), including a timer for measuring a time duration of the output signal (64), outputs a ring detection signal (66) when the time duration exceeds a predetermined time interval value, which is substantially less than a full ring cycle. A line switch (16) responsive to the ring detector (10) is provided to direct communication signals to a telecommunications device (18, 20, 22, 24, 26).</p> |
