| 摘要 |
TRUNK DIALING CONVERTER A digital FSK trunk dialing converter including M and E lead control is disclosed. The dialing converer further includes an FSK detector which is responsive to consecutive half period intervals of a received FSK signal, and a digital signal-to-noise (S/N) detector or estimator which operates to inhibit or keep the E-wire signal lead deactivated in the presence of noise signals which are received from the communications link in absence of acceptable FSK signals. The FSK detector is comprised of two digital circuits which generate pulses indicative of whether the received FSK signal is greater or less than the FSK center frequency. The pulses are integrated and used to trigger a flip-flop which provides a demodulated digital FSK output indicative of a received high or low FSK analog frequency. An E-wire control signal is generated in the receive logic circuitry in response to the demodulated FSK output. The S/N detector comprises a digital circuit coupled to the FSK detector and is responsive to the pulses generated thereby to generate reset signals which are coupled to logic circuitry when noise signals are received to prevent the generation of an E-wire signal when noise is present. |
