Abstract: A wireless audio distribution system may have a wireless transmitter, responsive to a plurality of audio input channels, for transmitting signals carrying the audio, a receiver, responsive to the transmitted signals for selecting one or more of the audio input channels to be reproduced in accordance with local setting selectors at the receiver. Speaker audio channel anti-noise signals can be subtracted from the head audio channel to cancel the noise related to the playing of the speaker audio on the speakers while the headset audio is played on the headset. Analog anti-noise signals can be produced by use of a microphone associated with the headset and later subtracted from the headset audio.

Abstract: A wireless audio distribution system includes a wireless headset for receiving a serial, digital bitstream including control data interspersed with digital data related to the audio channels, a manual audio channel selector switch; a manual volume adjustment control, an error detector and a muting circuit selectively reducing the volume level of the audio reproduced by the wireless headset in multiple steps based on errors detected by the error detector.

Abstract: A wireless audio distribution system includes a wireless headset for receiving a serial, digital bitstream including control data interspersed with digital data related to the audio channels, a manual audio channel selector switch; a manual volume adjustment control, an error detector and a muting circuit selectively reducing the volume level of the audio reproduced by the wireless headset in multiple steps based on errors detected by the error detector.

Abstract: The present invention is directed to methods and apparatus for enabling a subscriber to pre-purchase usage time from a telephone company or a consolidator at substantially a discounted rate and use the pre-purchased usage time against subsequent long distance telephone calls.

Abstract: The compression of composite video data is provided in order to reduce bandwidth and thereby increase the amount of bandwidth available for transmission. Composite video signals that include a plurality of fields are received at a selected clock frequency. A first selected number of fields is stored and a second selected number of fields is dropped. In a Frequency Division Multiplexing mode, the data is read out at a fraction of the selected clock frequency corresponding to the stored portion. In a Time Division Multiplexing mode, the data is read out at the selected clock frequency during selected intervals having a duration corresponding to the time it took to receive the stored fields. No data is read out during an interval having a duration equal to the time it took to scan the dropped fields, such time being allocated to the compressed information from other users of the same shared transmission medium.

Abstract: An apparatus and method for centralized processing of PIP images from a plurality of digital video sources includes a centralized processing device having a plurality of service drivers for outputting digital video data representing full screen images, and samplers for selectively sampling the data from the service drivers to form reduced screen images. A PIP bus channels the sampled data for access by various users. The sample data is selectively stored in buffers and is output to a display device when triggered by input/output triggers. The triggered output data representing reduced screen images is then combined by a video switch to form picture-in-picture images.

Abstract: A method and device for increasing the bandwidth of a drop line in a power line carrier communication system for facilitating high speed transmission of communication data. The drop line is divided into two sections, each containing both high frequency communication data components and low frequency power components. A high pass filter is provided for passing the high frequency components to a receiver device and a low pass filter is provided for passing the low frequency power components to an electrical system in a residence. The low pass filter is also used for blocking, from the drop line, high frequency noise generated by electrical appliances operating from the electrical system.

Abstract: A method and device for use with a communication system having a single cable line containing externally transmitted data within a fixed frequency band for providing interaction between a transmitting terminal device and a receiving terminal device without disrupting the externally transmitted data. A modulator is provided for shifting a signal generated by the transmitting device to a frequency not receivable by the receiving device. A low pass filter passes the shifted signal to a block converter which converts the signal to a frequency outside of the fixed frequency band but which is receivable by the receiving device. An amplifier is provided for amplifying the converted signal and the externally transmitted data for receipt of the amplified signal by the receiving device.

Abstract: An improved security system, including a protable smart card and a host computer, eliminates the need for the computer to store individual personal identification (ID) numbers for each user seeking access to the computer. Instead, the computer stores a first encryption algorithm E.sub.1 used in converting a particular identification number (ID).sub.n into a secret code S.sub.n for that particular user. S.sub.n also exists within the memory of the smart card having been loaded into its memory at the time of issue. A challenge number C is generated by the computer and transmitted to the smart card. Within the smart card and the computer, microprocessors respond to the challenge number C, the secret code S.sub.n, and a second encryption algorithm E.sub.2 in order to generate response numbers R.sub.n and R.sub.n ' respectively. Thereafter, R.sub.n is transmitted to the computer where it is compared with R.sub.n '. A favorable comparison is necessary for gaining access to the computer.