John D Ritchie

US Patent:

57905231, Aug 4, 1998

Filed:

Jul 31, 1996

Appl. No.:

8/690628

Inventors:

John A. Ritchie - Duluth GA
Steve Idler - Bolingbrook IL
Gregory T. Dubberly - Atlanta GA

Assignee:

Scientific-Atlanta, Inc. - Norcross GA

International Classification:

H04J 116

US Classification:

370241

Abstract:

A test system for evaluating the operating state of a headend of a broadband communications network for communicating telephony signals between a telephony system and subscribers of communications services. Modulators at the headend transmit telephony signals in the forward band of the broadband communications network. The forward telephony channels are demodulated and demultiplexed by a plurality of subscriber terminals into individual telephony signals directed to an addressed subscriber. Signals returning from subscribers are digitized into standard telephony signals onto the reverse band of the broadband communications network, and demodulated by demodulators of the headend into a standard telephony signal that is interfaced to the telephony network. The test system evaluates the operating state of a selected demodulator of the headend by modulating a carrier with a predetermined data pattern to generate a upstream test signal. The upstream test signal is transmitted to the selected demodulator, which responds by outputting a detected upstream test signal.