Abstract: A method and apparatus for minimizing multipath interference for commercial FM signals which use SCA secondary signals in QAM format that includes tracking the time series of phase measurements of a received stereo pilot signal for determining the proper phase reference for demodulation of QAM signals at the center of the time series. Phase measurements of the pilot signal are tracked over a predetermined tracking period. The phase measurement is used to support demodulation of the QAM signal. The SCA secondary signals in QAM format transmitted on commercial FM have minimal multipath interference and Doppler interference by movement of transmitter and receiver (vehicular).

Abstract: An audio signal amplifier circuit includes an external output terminal of an IC to which an output line of a power amplifier circuit is connected, a first resistor connected between a certain terminal of the IC other than the external output terminal and a feedback input of a differential amplifier circuit, a first capacitor connected between the external output terminal and a loud speaker, a second capacitor between the certain terminal of the IC and a wiring line between the external output terminal and the loud speaker, a filter circuit provided on a signal input side of the differential amplifier circuit and including a second resistor and a third capacitor for attenuating signal components having frequencies in a middle and high frequency ranges and voltage follower means provided between an input stage and an output stage of the audio signal amplifier circuit, wherein the first capacitor is a small capacitor having a capacitance value in the order of 30 &mgr;F or smaller and an attenuation characteristi

Abstract: Audio systems using a digital audio interface between a sender and a receiver are known. Due to the digital revolution, it is very easy to make copies of copyright protected work. By using a bi-directional control bus in the audio interface, it is made possible to send audio signals with a standard quality to “normal” receivers audio, and higher quality audio to receivers which are authorized to receive higher quality audio.

Abstract: An active noise suppression system for use in noisy environments includes a dual microphone noise suppression system in which the echo between the two microphones is substantially canceled or suppressed. Noise is cancelled by the use of first and second line echo cancellers, which model the delay and transmission characteristics of the acoustic path between the two microphones. In a first embodiment, a noise suppression system acts as an ear protector, canceling substantially all or most of the noise striking the dual microphones of the ear set. In a second embodiment, a noise suppression system in accordance with the present invention acts a noise suppression communication system, suppressing background noise while allowing speech signals to be heard by the wearer.