Amaf Industries, Inc.

Trw Limited

James H Leveque

John Eldon

Frederick A Williams

A digital FSK trunk dialing converter including M and E lead control is disclosed. The dialing converter 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.

Trunk dialing converter

A method and apparatus for reducing noise fluctuation in a linked compressor-expander (Lincompex) telecommunications system in which an artificial tone signal is injected into a demodulator of the communication system to bias the output toward self quieting. The artificial tone is developed to have a level that is effective below a threshold level of Lincompex demodulation such that during normal communication transmission, the artificial tone has no deleterious effect, while below the demodulation threshold, random noise inputs are effectively biased to a constant level to produce a quieting effect on the demodulator output.

Method and apparatus for reducing noise in a linked compressor-expander

Complex waveforms may be transmitted using Lincompex techniques by frequency shifting either the complex waveform, its envelope, or both, in order to ensure that the compressed complex waveform and the envelope signal are transmitted without any substantial overlap therebetween utilizing Lincompex techniques. Overlap between the compressed waveform and envelope prevents the proper demodulation of the complex waveform from the signal transmitted. Accordingly, the frequency shifting techniques utilized in the present application allow Lincompex techniques to be utilized with complex waveforms having both a large bandwidth and a large envelope bandwidth, for example, the waveforms generated by parallel tone or multi-tone digital data.

System and method of transmitting a complex waveform over a

A digital linked compressor-expander telecommunications system (Lincompex), is implemented using a general purpose digital signal processor wherein the compression and expansion functions are performed by blocks of programmed code. Input audio analog signals are converted to parallel data digital signals thereupon the digitial signals are input for processing. After processing, the resultant signals are passed to a 16-bit digital-to-analog converter where either the compressed or expanded digital voice data signal is converted back into an audio frequency analog signal for either transmission or communication on an output device.

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Ellicott City, MD, United States of America

James H Leveque