Abstract: A headend method and apparatus for a digital transmission system is provided which includes inputs for receiving first and second program information from first and second program sources and inputs for receiving first and second control information from first and second control sources. The first and second program information is applied to a switching circuit and a switch control controls the switching circuit to output channels of program information comprising combinations of the first and second program information for output to a subscriber. Processing circuitry allows for selectively providing the first and second control information to the channels output from the switching circuit.

Abstract: A method of transferring a data message from a remote unit to a central location is provided. A plurality of data channels is selected for transmitting the data message from the remote unit to the central location. At least one random transmit time is generated for transmitting the data message for each of the plurality of data channels. The data message is transmitted over the plurality of data channels at the transmit times. An apparatus for transferring a data message from a remote unit to a central location is also provided.

Abstract: A dynamic global callback technique which is capable of maintaining a manageable number of incoming calls to a central location from a plurality of remote units. A plurality of remote units are prompted to initiate callback attempts to a central location during a given callback period. The number of successful callback attempts from the remote units to the central location is monitored. The callback period if dynamically adjusted so as to cause the monitored number of successful callback attempts to approximately equal the number of successful callback attempts capable of being handled by the central location without overloading the telephone network.

Abstract: Automatic level calibration apparatus for transmitting data from a cable television terminal to the headend of a cable television system comprises programmable transmitter apparatus of the terminal, programmable receiving apparatus at the headend and a calibration controller. Responsive to an addressed command from the headend, the programmable transmitter apparatus returns a sequence of levels at a particular calibration frequency. The programmable receiver apparatus determines an indication of the received signal strength of each of the levels of the sequence of levels. The controller determines an optimum level for transmissions from the terminal.

Abstract: A dynamic global callback technique which is capable of maintaining a manageable number of incoming calls to a central location from a plurality of remote units. A plurality of remote units are prompted to initiate callback attempts to a central location during a given callback period. The number of successful callback attempts from the remote units to the central location is monitored. The callback period if dynamically adjusted so as to cause the monitored number of successful callback attempts to approximately equal the number of successful callback attempts capable of being handled by the central location without overloading the telephone network.

Abstract: An impulse pay-per-view system wherein a number of downloadable transactions may be utilized to effect increased control and diversity is disclosed. A preview time/free transaction permits a system subscriber to view portions of a pay-per-view event without purchasing the event. A security transaction sent while a pay-per-view event is active may be used to prevent a subscriber from receiving events which have not been purchased. A telephone number transaction may include a special character representing an instruction to pause between the dialing of selected digits. A viewer statistic transaction may be use dot instruct a subscriber to record the channel he is viewing. Finally, a subscriber may pre-buy pay-preview events in order to facilitate VCR recording of the events while he is asleep or away from home.

Abstract: Apparatus for transmitting and receiving a period shift keyed data stream comprises a data processor such as a microprocessor which may control the generation of the waveform as well as the determination of the bit values of an incoming signal. When the data to be transmitted comprises a plurality of data values, each data value is represented by a different predetermined frequency. Further, each data value is represented by the transmission of the predetermined frequency for a predetermined transitionary interval plus one cycle or period. One portion of the transitionary interval precedes and the remaining portion follows the one cycle. For example, the data value may be represented by a three cycle burst of frequency such that, in determining the represented data value, two cycles of transitionary interval are detected but ignored and the central cycle of the three cycle burst is timed for determining the data value by edge detection techniques.

Abstract: A method of preventing a power failure from corrupting data being written to a non-volatile memory. Before a write operation is performed, information is written to a double buffer to reconstruct the steps that will be performed during the write operation. A flag is set indicating that the information in the double buffer is accurate. The write operation is then performed and the flag is cleared. The double buffer is dynamically moved throughout the non-volatile memory to distribute the wearout of the non-volatile memory as evenly as possible.