Abstract: An automated digital broadcast system which is capable of reliable operation for long periods of time without human assistance. The system comprises a plurality of compact disc players or other audio devices which are controlled by computer to sequentially play a predetermined list of musical selections and commercial or informational messages.

Abstract: A novel and improved automatic gain control (AGC) circuit which is ideally suited for use with sound systems which are operated in a very large environment, such as a supermarket or auditorium. The preferred embodiment of the circuit comprises first and second input channels and a single output channel. The first input channel is a feedback signal provided by a microphone which is placed near one of the speakers of the sound system. The second input channel receives a music signal which is being played by the sound system. The output of the circuit is a music signal which has a constant ratio relative to the noise detected in the environment. Constant power ratio operation of the system is achieved through the use of logarithmic processing of the signals in each of the respective input channels. Control circuitry is provided to maintain the gain level of the system at a constant level during periods of time when no music is present on the second input channel.

Abstract: An acoustic transducer array includes a number of transparent continuous aperture transducer elements which are aimed at various angular sectors in a field of view and are embedded in an acoustically transparent material such as casting resin. Each transducer provides a beamformed output, and the transparency of the elements ensures that each element observes an acoustic field that is unperturbed by the other elements. A high resolution and a wide field of view are obtained by overlapping the transducer elements so that each element captures an increased area of acoustic signal. Preferably, the transducer elements are cut from thin, flexible metalized sheets of voided piezeoelectric polymer such as polyvinylidene fluoride or polyvinyl fluoride co-polymer. The polymer transducers are broad band in nature, and permit multiple frequency, multiple beam sonar configurations.

Abstract: Apparatus for generating a signal indicative of the phase of a selected pulsed single frequency signal in a background of noise. A first averaging phase detector generates the average phase of the selected signal. A second averaging phase detector generates the average phase of a quadrature signal. Pulse phase averagers compensate for noise in the average phases. A quadrature logic section selects the first average phase when it varies linearly, and selects a phase proportional to the guadrature phase when the first phase varies non-linearly.