| 摘要 |
<p>Method and apparatus for non-linearly filtering impulse and low frequency noise received over a network so as to avoid false activation of equipment is disclosed. A squelch circuit assures that only multiple transitions of at least three half-cycles in the received waveform of a proper frequency and amplitude will activate the receive while a single half-cycle, although of a proper frequency and exceeding the threshold, will not falsely activate the receiver. RC circuits provide a variable delay in the squelch portion of the filter to suppress impulses. In an alternative embodiment, double half-cycles will not falsely activate the receiver. Emitter-coupled logic (ECL) circuitry is preferably employed to provide speed adequate for ten-million bit per second transmissions.</p> |
