General Instrument Corporation

Rockwell International Corporation

General Instrument Corporation of Delaware

Tocom Corporation

Thomas F Martin

John S Chenoweth

Dale Gleitz

John P Fullingim

Paul R Tinguely

Carl F Schoenenberger

Kevin G Cordle

James E Austin

Harvey Rogers

Robert W Storey

John Fullingim

John Stephen Chenoweth

A system transmits two audio services, each related to a different video program, within the bandwidth typically reserved for a single audio channel. Each audio service may be processed as a mono, stereo or encrypted signal prior to modulation onto its own audio carrier. The two audio carriers are summed together and applied to an RF modulator. The frequencies of the audio carriers are selected to ensure that the quality of the video program is not degraded, the video channel mask bandwidth is not exceeded and interference from the unselected audio carrier is negligible.

Audio transmission method for channel doubling system

Video signal scrambling and descrambling methods and apparatus for a subscription TV system are provided which are compatible with other equipment operating in accordance with pre-existing modes of signal scrambling and descrambling. Coded indicator signals generated in accordance with the invention are inserted into selected lines of video signals before they are scrambled by a previously installed scrambler located at a central office. The scrambled video signals, with indicator signals inserted, are then sent to all subscriber locations within the TV system. At new subscriber locations, descrambling receivers, in accordance with the present invention, detect and decode the indicator signals and in accordance with a new mode of operation properly descramble the video signals. At old subscriber locations, previously installed descrambling receivers ignore the indicator signals and descramble the video signals in accordance with pre-existing modes of operation.

Subscription television picture scrambling and descrambling system

Apparatus is provided for switching traps in and out of a cable television signal path. A plurality of double pole double throw switches is connected in series with the signal path. Each switch has a first actuated position, a second actuated position, and an off position. The switches connect corresponding traps to the signal path in the first actuated positions. In the second actuated positions, the switches provide a through connection in series with the signal path. An open circuit is provided along the signal path when a switch is in the off postion. Actuation and disconnect signals transmitted over the cable television network selectively actuate the switches to the frist, second, or off positions. The switches are constructed of solid-state components such as diodes, and are actuated by unipolar biasing signals.

Signal switching apparatus

Remote control of subscriber access to premium programs on a cable television system or the like is provided. A signal path carriers program signals received from a cable television system. A switchable port coupled to the signal path is identified by a logical channel number. First data are received and stored from the cable television system assigning a service code to the logical channel. Second data are received and stored from the cable television system identifying authorized service codes. The assigned logical channel service code is periodically compared to the stored authorized service codes to determine if the logical channel is authorized. The port is switched to provide or deny access to a program signal carried on the signal path, depending on whether the service code assigned to the logical channel identifying the port is authorized. A plurality of ports can be provided to enable subscriber access to different premium services. Each port can couple a trap to the signal path, alternately bypass the trap, or alternately open the signal path to disconnect a subscriber.

Addressable control system for CATV program distribution

Frequency control of multiple oscillators using a single frequency locked loop is accomplished by a single frequency-control device that is time-shared with a plurality of voltage-controlled oscillators and selectively establishes a 'desired' frequency for each oscillator. The output of each oscillator is, in turn, selectively routed to a frequency counter which measures the 'actual' frequency of the oscillator. A comparison between the desired frequency and the actual measured frequency for each oscillator is made, and an error voltage developed. This error voltage is routed to the appropriate capacitor, which stores the voltage required to keep the selected oscillator on frequency until the next time it is measured.

Method and apparatus for frequency control of multiple oscillators using

A cable television channel selector/descrambler enables the full capabilities of a cable-ready video appliance (e.g., television set or VCR) to be used in conjunction with a cable television system providing unscrambled channels and scrambled premium channels. A broadband cable signal containing a plurality of television signal channels having different frequencies is passed through a filter to produce a modified cable signal having one of the signal channels removed therefrom. The broadband cable signal is input to a tuner for selectively tuning only to scrambled signal channels contained in the broadband cable signal. The tuner is tuned to a scrambled signal channel to be viewed by stepping through the scrambled signal channels accessible by the tuner until the desired signal channel is reached. A scrambled signal tuned by the tuner is descrambled and remodulated to convert it to the frequency of the signal channel removed by the filter in producing the modified cable signal. The re-modulated descrambled signal is combined with the modified cable signal to form a composite signal for input to a video appliance. The composite signal contains all of the original unscrambled channels together with the selected premium channel which has been descrambled.

Cable television channel selector/descrambler for use with cable-ready

A multiple converter system is provided for a remote user in a cable communications system. The converters at the user location are linked together via a splitter. One converter operates as a master converter transmitting a master control signal to the other converters, designated as slave converters. The slave converters are actuated only upon reception of the master control signal. The master control signal is interrupted by the master converter only when it transmits data upstream to the central office or when one of the slave converters is required to transmit data. A slave converter notifies the master converter of the need to transmit data by a slave signal. A transmitter unit is automatically activated for transmitting data upstream upon the absence of the master signal on the bus.

Master/slave converter system

A VCO (Voltage Controlled Oscillator) is provided with a full set of tuning voltages from a reduced number of reference voltage sources, such as potentiometers. Logic controlled switch means delivers any of the reference voltages individually or predetermined combinations thereof as the tuning voltages to the VCO. A reference voltage source potentiometer is provided for each of the odd numbered tuning voltages, and a piecewise linear approximation is provided for the intermediate even numbered tuning voltages by generating the average of two adjacent odd voltages.

Voltage controlled oscillator with reduced number of tuning

A voltage dividing and reference circuit for creating a pseudoground from a unipolar power supply such that when used in combination with a digital voltmeter circuit a bipolar input signal can be measured for both polarities with respect to ground.

Growing community of inventors

Richardson, TX, United States of America

Thomas F Martin