Patent ID: 8170473

Claim:
A communication system comprising: a repeater comprising: circuitry for applying a secondary signal to the primary signal passing therethrough, wherein the secondary signal is a function of the primary signal and a known distortion, and wherein the known distortion identifies said repeater; a transmitter for transmitting a combined signal, wherein the combined signal includes the primary signal and the secondary signal; a primary receiver comprising: a receiver for receiving the combined signal; and circuitry for extracting the primary signal from the combined signal; a secondary receiver comprising: a receiver for receiving the combined signal; circuitry for receiving the primary signal from said primary receiver; circuitry for applying an inverse function to the combined signal and the primary signal to retrieve the known distortion; and circuitry for determining whether the combined signal was received from said repeater by a comparison of the known distortion and one of a set of known distortions.