Patent ID: RE40038

Claim:
A circuit for receiving an input signal and providing a quantized output signal in response, said quantized output signal being at either a first level or a second level, and said input signal being substantially at either said first level or said second level, said circuit comprising: (a) an automatic gain control (AGC) circuit for providing a gain signal which processes said input signal to output a controlled signal having a constant amplitude at either said first level or said second level, said AGC circuit being operative in a first mode to provide said gain signal in response to the difference between the level of said controlled signal and the level of said quantized output signal; (b) a restorer circuit coupled to said AGC circuit for receiving said controlled signal and for providing said quantized output signal in response; (c) a carrier detect circuit coupled to said AGC circuit and having an input for receiving said quantized output signal, said carrier detect circuit providing a detection signal for indicating the presence of a transition in the level of said quantized output signal, said detection signal being coupled to said AGC circuit; such that during periods when said detection signal indicates that there are transitions in the level of said quantized output signal, said AGC circuit is operative in said first mode, and during periods when said detection signal indicates that there are no transitions in the level of said quantized output signal, said AGC circuit is operative in a second mode wherein said gate signal is continually increased, at least to a predetermined level.