| 摘要 |
<p>The disturbance monitor comprises a monostable (5) and a coincidence monitor (6). It is placed immediately following the limiting amplifier (4), and between it and the demodulator (9). The monitor acts on a gate (10) between the demodulator and the a.f. amplifier (11). During normal operation the limiting amplifier output is a square wave whose edges trigger the monostable (5) such that the coincidence detector (6), which also receives the same signal, gives a continuous logic high. A disturbance results in a missing edge leading to a logic low which activates a switching stage (7). This functions in conjunction with a counter (13) and opens the gate (10) if the disturbance persists for a predetermined time. The disturbance monitor has rapid response and provides good signal to noise discrimination even at low incoming signal levels.</p> |
