Abstract: A method for digital data distribution or broadcasting that takes advantage of non-deterministic (or “opportunistic”) unused bandwidth in dynamically optimized broadband digital broadcast systems. Digital data files received from broadcasts are stored in mass storage devices for viewing at a later time at high speed, overcoming “last mile” narrow bandwidth issues. Instead of reserving a particular communications channel or data transfer spectrum, data is opportunistically “piggybacked” onto unrelated broadcasts, using otherwise unused bandwidth within existing broadcast channels or spectrums. The broadcast source does not target the digital files at specific identifiable users or broadcast contents based on their interactive requests. Data broadcasting in accordance with the present invention may be implemented to work with any medium which allows the delivery of large files in a one-to-many fashion (i.e.

Abstract: An asynchronous FSK modulator-demodulator (modem) having a capability of operating at data rates of 300, 600 and 1200 bits per second in a voiceband telephone channel is compatible with the specifications of the Bell 103/113, Bell 202, CCITT V.21 and CCITT V.23 modem types. The modem according to the invention is incorporated into a single integrated circuit to minimize external components in a system. The modem is pin programmable, that is, the mode and speed of operation is defined by a parallel digital data signal applied to device terminals. Digital signal processing techniques are employed to perform all major functions, including modulation and filtering. Multiplication functions are performed without need for multipliers by employing shift registers and canonic sign arithmetic. Analog-to-digital conversion and digital-to-analog conversion circuits are incorporated into the device.

Abstract: In a digital data communication receiver, an apparatus for estimating the time of zero-crossing between successive samples of a continuous frequency shift keyed (FSK) or like zero-crossing signal in a manner more accurate than is provided by the basic sampling clock. The apparatus includes means for sensing a change in sign relative to successive samples of the signal and means responsive to the sensed sign change to interpolate between the values of the respective samples for indicating more accurately the time of occurrence of the zero-crossing prior to the second sample, thereby demodulating the continuous signal.