Patent ID: 8335326

Claim:
A communication system for encoding and decoding communication signals for use within an audio amplifier equipped with a vacuum tube replacement device (VTRD), wherein the audio amplifier includes an audio input for interfacing with externally supplied audio signals, the system comprising: an audio processing system that is externally located with respect to the audio amplifier equipped with the VTRD, wherein the audio processing system is arranged to receive an analog audio signal when input to the communication system and provide a processed analog audio signal that has an audio energy located in an audible frequency band; a code modulator that is externally located with respect to the audio amplifier equipped with the VTRD, wherein the code modulator is arranged to encode an address signal and a command or data signal into an envelope modulated carrier signal, wherein the address signal and the command or data signal are encoded in one or more frequencies associated with a carrier signal that has a carrier signal energy located in a supra-audible frequency band, and wherein the envelope modulated carrier signal corresponds to an envelope modulated version of the carrier signal that has an envelope with an envelope energy located in a sub-audible frequency band; and a mixer that is externally located with respect to the audio amplifier equipped with the VTRD, wherein the mixer is arranged to combine the envelope modulated carrier signal with the processed analog audio signal to generate a combined signal for communication to the VTRD in the audio amplifier, wherein an output of the mixer is coupled to the audio input of the audio amplifier such that the combined signal is coupled into the audio input of the audio amplifier for receipt by the VTRD in the audio amplifier, wherein the audio input of the audio amplifier serves as both a communication port and an audio input port for the VTRD without modifying the audio amplifier.