Abstract: An optical superposition network that utilizes a time division multiplexing (TDM) protocol includes a first optical transmitter, a second optical transmitter and a receiver. The first optical transmitter transmits information in a tertiary mode during a time slot. The second optical transmitter transmits information in a tertiary mode during a different time slot. The information transmitted across the optical superposition network has an approximately constant average intensity such that the receiver can utilize a single decision threshold for the information received from the first and second optical transmitters.

Abstract: A central digital signal radio processor (DRSP) is separated from all analog inputs and outputs by digital data links. Each end of a data link couples to an interface which has transmit and receive capability using cancellation techniques to allow full duplex transmission. An antenna module located at the antenna processes much of tuning functions in analog and then converts the signal to digital and sends it to the DRSP for further processing. Transmitted digital signal from the DRSP are converted to analog by the antenna module and sent to the antenna. Microphones, tape and CD players and other inputs are similarly linked to the DRSP. The DRSP digital audio output is sent to speaker modules which convert to analog signals for driving speakers.

Abstract: A radio with a tuner and other program sources uses a digital signal processor (DSP) to enhance the audio signal and to generate a stream of digital data including audio data and control data corresponding to loudness functions. A fiber optic data link couples the data stream to a plurality of remote DSP modules each of which drive one or more speakers. Each module contains a user programmed DSP, a digital to analog converter and an amplifier for each associated speaker. The DSP modules are identical except for software parameters which establish a transfer function and a loudness characteristic for each speaker. The same DSP modules and the same speakers can be used in several vehicle types and the system audio performance can be optimized by customizing software for each type of vehicle.

Abstract: A digital phase-lock loop network that provides input and output clock signals to a digital data receiving system generally, and particularly to a data buffer contained therein, is disclosed. The digital phase-lock loop network provides bit-clock synchronization using a fixed input clock and an output clock having a variable frequency that is adjusted to correspond to the average input rate of the data samples into the data buffer. The digital phase-lock loop network allows the data buffer to be operated as a temporary storage device maintaining a nominal number of data samples therein at all times by avoiding any overflow and underflow data handling conditions that may otherwise cause loss of data. The digital phase-lock loop network of the present invention is particularly suited for the Eureka-147 system which has become a worldwide standard for digital audio broadcasting (DAB) technology.