Patent ID: 7254194

Claim:
An apparatus for processing a differential first pulse amplitude modulated (PAM) signal having a time varying magnitude representing a sequence of integer-valued first data elements, the apparatus comprising: amplifying means for amplifying the first PAM signal with an adjustable first gain to produce a second PAM signal; digitizing means for processing the second PAM signal to generate a sequence of second data elements having values representing magnitudes of the second PAM signal at a succession of times; and first automatic gain control (AGC) means for determining a number of second data elements generated per unit of time having values within a first range and for adjusting the first gain when the determined number falls outside a second range wherein the first AGC means comprises: first means for generating a counter data of value representing a count of second data elements within a succession of N data elements having values falling within the first range, where N is an integer greater than 1, and second means for adjusting the first gain when the value of the counter data falls outside the second range; wherein the first means comprises: means for generating an output data in response to each second data element, the output data being of value indicating whether an absolute value of the second data element resides within the first range; a first counter receiving the output data, for altering the value of the counter data in response to each pulse of a periodic clock signal (CLK) depending on whether the output data is of value indicating that the absolute value of the second data element resides within the first range, and for setting the value of the counter data to zero upon receipt of each pulse of a first control signal; and means for supplying a pulse of the first control signal to the first counter in response to every Nth pulse of the clock signal.