Abstract:
An audio signal coupling and processing system utilizes the electronics and speakers of a high fidelity system for reproduction of TV audio without direct connection between the television set and the high fidelity system. Partially processed FM signals of fixed center frequency radiated from the audio IF section of the television receiver are sensed by the system which processes the signals and transmits them for receipt by an FM receiver within the high fidelity system, the transmitted signals having a nominal strength allowing clear reception by the FM receiver without violating broadcasting regulations. The system includes a first antenna tuned to receive the radiated FM audio signals from the television receiver, circuitry for demodulating, de-emphasizing and then pre-emphasizing the sensed FM audio signals, an FM modulator for frequency modulating about a carrier frequency at a selected point within the 88-108 megahertz band, and a second antenna for transmitting the resulting frequency modulated signal to the FM receiver. The FM modulator utilizes an unbiased transistor to provide a variable capacitance to the frequency determining coil of an oscillator, and the system includes a circuit for indicating whether the FM audio signals received by the first antenna are of at least minimum strength.