Abstract: A hybrid coaxial cable network employing interdiction to ensure privacy in telephony communications. The video and telephony signals are secured such that telephony and interactive video signals to and from a subscriber do not appear on the network at any other undesired subscriber location.

Abstract: The inherent structure of redundant information fields contained in the message format of a multifrequency communication system is utilized to determine if the information on the individual hops has been degraded due to interference. By detecting bit errors in the received data sequence and identifying the frequencies on which signals representing the bits in error were transmitted, one can block out data from those frequencies on a dynamic basis. The received data sequence is correlated against the possible code words that might have been transmitted. The result of this correlation is a decision by the receiver that a particular code word was transmitted. Then, the code word that the receiver decides was transmitted is compared against the received data sequence and bit errors are identified. Finally, by knowing the relationship between the transmission frequencies and the order of the received bits, the receiver can identify the frequencies on which signals representing the bits in error were transmitted.

Abstract: An electromagnetic test system induces large current pulses in a component of a system under test. The pulse waveform may be selectively varied, and possible waveforms include square wave pulse, double exponential, and damped sinusoid waveforms. In a preferred embodiment, these waveforms are generated by simultaneously triggering a plurality of modular signal injector units having ferrite cores hinged to permit positioning of a system component under test (such as a cable or antenna) along their central axes without disturbing connections of the tested component within its system. The injector units are resonance tuned to induce a particular signal in the component under test when triggered, and the modular construction of the system permits selective connection of different injector units to provide different desired total induced signals.

Abstract: A frequency generating means, generates an initial frequency of greater amplitude than the amplitude of a television signal carrier wave. The generated frequency is compared to a reference frequency which would be suitable for jamming one of the channels to be jammed. If the generated frequency is too high or too low, the frequency generating means generates a new frequency which is, respectively, either lower or higher than the initial frequency it generated. If the new generated frequency is still higher or lower than the reference frequency, the frequency generating means generates another new frequency, which is respectively, either lower or higher than the previously generated frequency, but by a lesser amount than the amount by which the previously generated frequency differed from the frequency generated before it. The generation of new frequencies continues until one of them is within a desired range of the reference frequency, at which time the generated frequency is stored in memory.

Abstract: A system for producing an oscillating signal includes a phase-locked loop including a control voltage producing circuit. The control voltage producing circuit is provided for producing a plurality of predetermined control voltages, with each of the predetermined control voltages corresponding to a desired frequency. A plurality of memories are provided in the phase-locked loop for storing the predetermined control voltages. A control device is connected to the plurality of memories for storing the predetermined control voltages in the memories in a state where the phase-locked loop is closed, and for deriving at least one of the predetermined control voltages stored in the memories in a state where the phase-locked loop is opened. A voltage-control oscillator is provided in the phase-locked loop to be operated by the predetermined control voltage derived from one of the memories for producing the oscillating signal having a desired frequency dependent upon the desired voltage.

Abstract: Television service denial apparatus comprises a microprocessor controller for controlling the generation of a control signal waveform. The control signal toggles a program denial device between first and second conditions. The program denial device, responsive to the control signal waveform, only periodically outputs a television signal spectrum to which a sophisticated television receiver be a device having only 20 dB of signal isolation. In one embodiment, the program denial device comprises a signal modulator for modulating an incoming television signal spectrum including one continuous wave carrier channel having no superimposed video. A character generator, responsive to the microprocessor, generates a control signal waveform for controlling the operation of the signal modulator.

Abstract: A transmitter/receiver system is provided wherein a transmitter of such system produces a transmitted signal frequency modulated in accordance with the level of a modulating signal and a receiving antenna has an output thereof coupled to a receiver through a switch means, for coupling or inhibiting signals received by the receiving antenna from passing to the receiver selectively in accordance with the level of the modulating signal.

Abstract: A method and apparatus for providing periodic subscription television services comprises a way for subscribers who cannot afford the fees for full time television services such as a regular cable television service to obtain subscription service to a plurality of allocated channels on a periodic basis. The method comprises the steps of allocating channels to a periodic service offering and storing in memory of service denial apparatus service code data which represents the allocated channels. The service denial apparatus for providing periodic service comprises a service denial device such as a switch 389 or other circuit controlled by a controller 260 of service denial apparatus for periodically closing and opening service lines to the periodic service subscriber in accordance with predetermined periodic service intervals.

Abstract: A system for preventing the remote detection and decoding of computer data from RF or conducted signal emissions is disclosed. A simulator is coupled to the computer for emulating signal emissions in order to mask the computer signal emissions. The simulator includes an emulation generator coupled to the computer to radiate signals that fully emulate those radiated by the computer to be protected. The emulated signal emissions are synchronized with the computer signal emissions by a special control unit which receives timing instructions from the computer. A random sequence generator randomizes and convolutes the sequence of the emulated signal emissions so that the composite signal emissions formed by the computer and the simulator cannot be decoded to render meaningful data indicative of that being processed by the computer. The simulator is coupled with a computer to be protected by connection to the I/O interface port of the computer.

Abstract: Off premises cable television interdiction apparatus comprises a microprocessor actuation and control means for actuating and controlling at least one frequency agile voltage controlled oscillator. The voltage controlled oscillator selectively jams only unauthorized premium programming transmitted in the clear from a headend to a particular subscriber. The voltage controlled oscillator generates a jamming signal carrier at a frequency 1/N between the video and audio carriers where N is an integer, preferably small. The microprocessor provides a calibration mode and a normal mode of operation. During the normal mode of operation, a frequency hopping rate on the order of four thousand hertz is achievable. the method of interdiction comprises the steps of generating and storing voltage control words for operating the oscillator consistent with a headend selected jamming factor for a particular channel to be jammed and addressably transmitted and stored premium programming authorization data.

Abstract: An off-premises method and apparatus for the interdiction of unauthorized channels of a broadband cable television signal includes common circuitry for adjusting the amplitude and equalization levels of the broadband CATV signals and one or more subscriber modules for generating jamming signals of different frequencies which are used to interdict one or more unauthorized channels. Each subscriber module is associated with a subscriber and is programmable and addressable to adjust the jamming parameters of that subscriber independently of other subscribers. Each subscriber module circuit comprises a plurality of latches, each of which is associated with one of a plurality of digital to analog converters. Each of the digital to analog converters drives one or more frequency agile oscillators with its analog output to generate the jamming signals.

Abstract: Method and apparatus for reducing the effects of noise jamming on coherent frequency or phase modulated signals employs a two channel radio signal processing system (15, 20) which accepts an input signal containing a desired signal (S) and a jamming signal (J) from a receiver input circuit (10). In the first channel (15), a hetrodyne mixer (30) and wideband filter (35) select the difference frequency component between the jamming signal and the desired signal [X(t)] while in the second channel (20), a local oscillator (45), mixer (50) and filter (55) function to select the difference frequency between the jamming signal and the local oscillator [Y(t)]. A third mixer (90) and bandpass filter (95) combines the outputs X(t) and Y(t) to provide the desired signal, including its original phase and frequency modulation components substantially independent and free of the jamming signal, to the receiver output circuit (12).

Abstract: A modular data link having a transmit processor for receiving input data and for providing different portions of the input data at each of a plurality of outputs. A plurality of transmit channels each receive an input data portion and transmit a signal corresponding to the received input data portion. An antenna collects the transmitted signals and provides an output thereof. A plurality of received channels each receive the collected signals from the antenna and extract a different input data portion from the collected signals. A receive processor having a plurality of input each coupled to a respective receive channels receives the extracted different input data portions so as to recombine the different input data portions in regenerating said original input data as output data.

Abstract: In order to protect computers and the like against the pick up, the recording and the unauthorized use of data from the computers during the working thereof, and to protect them against high energy transient disturbances taking place on the main A.C. power line, a filter unit (1) is foreseen comprising a plurality of sections (19) comprising inductances (21) and capacitances (23), between which it is interposed at least a gas-discharge surge arrester (25) and varistors (27), and masking unit (3) comprising a power supply (31), a white noise generator (33) and an amplifier (35) emitting from the antenna circuit (61) said properly amplified white noise which is completely random and unpredictable, and therefore impossible to be decoded.

Abstract: A off-premises CATV system includes a compensation control including a picture carrier controlled automatic gain control and an automatic slope control. A broadband television signal output from a variable gain device is distributed by a radio frequency signal splitter to a number of subscribers for interdiction by the generation of a number of jamming signals. The variable gain device and a variable impedance device which is frequency dependent are connected in series for automatic gain control and automatic slope control, respectively. A first feedback control is used to compare a first portion of the broadband television signal to a reference power level and to control the variable gain device to null the error. A second feedback control is used to compare a second portion of the broadband signal to a second reference power level and to control the variable impedance device to null the error.

Abstract: A communication system (100) has at least one base site (204) which includes a plurality of transceivers (110A-C) operating on a plurality of communication channels for communicating to at least one of a plurality of communicators (108). The at least one base site (204) comprises a generator (210) generating a plurality of interference signals according to a predetermined pattern on a subset of the plurality of communication channels. A processor (208) initiating and terminating communication between the base site (204) and the at least one communicator (108) on a selected communication channel substantially free of interference signals. The processor (208) further determines the communication channel being selected, and determines whether to change the predetermined pattern of the plurality of interference signals.

Abstract: This invention is a multiple-frequency signal generator apparatus and method primarily for simulating a cell site interference environment for electromagnetic communications systems. The generator can produce a plurality of frequencies having a frequency-spacing of d cycles per second. The invention comprises a single frequency multiplier, at least three oscillators and two mixers for providing a multitude of frequencies closely spaced about a carrier frequency. The simple design and components avoid complexity and save costs.

Abstract: In a extraneous of signal method of preventing detection of signal information from raster scan signals in a plurality of consecutive line signals intended to form an image or partial images there is generated a random signal sequence, correlated with the information-carrying raster scan signals, but without information content, which is transmitted as protection for the raster scan signals. An apparatus for this purpose includes a generator (10,12) adapted for generating a random signal sequence synchronous with the raster scan signals, and a switching element (5) adapted to transmit the random signal sequence round the equipment containing the raster scan signals that are to be protected.

Abstract: A system and method are disclosed for preventing intelligible interception of information signals transmitted over a two-direction line. A masking signal is applied through a hybrid circuit at the receiving end of the line, and this masking signal, which appears on the line together with the information signal, prevents the intelligible decoding. Only at the receiving end of the line, where the hybrid circuit attenuates the masking signal which it receives at its receive port, can intelligible decoding take place. Signal processing techniques used at the receiving end permit larger amplitude masking signals to be used, thus creating even greater confusion for an unauthorized detecting mechanism which is coupled to the line.

Abstract: Off premises cable television interdiction apparatus comprises a microprocessor actuation and control means for actuating and controlling one or more frequency agile voltage controlled oscillators. The voltage controlled oscillators selectively jam only unauthorized premium programming transmitted in the clear from a headend to a particular subscriber. Each voltage controlled oscillator is allocated a continuous band of frequencies consistent with the elimination of jamming signal frequency harmonics which may disturb authorized programming at a higher channel frequency. The microprocessor actuation and control means provides a calibration mode and a normal mode of operation. The method of interdiction comprises the steps of generating and storing voltage control words for operating the oscillators consistent with a head end selected jamming factor for a particular channel to be jammed and addressably transmitted and stored premium programming authorization data.

Abstract: A method and system for scrambled transmission of an information signal having a regular, repeating information rate from which a receiver of the information signal derives synchronizing information as in a television video signal. The information signal is summed with a scrambling signal having a frequency which is a function of the information rate plus an error quantity within a predetermined bandwidth, namely that of the synchronizing circuitry in the normal information receiver. The sum of the information signal and the scrambling signal is transmitted as the scrambled information signal. In a television scrambling system, the information signal is a television video signal and the information rate is a video synchronizing rate, preferably the horizontal line rate.

Abstract: In a secure communication system, a method for generating dummy traffic to forestall cryptanalytic attack by traffic analysis. Both the dummy traffic signal and certain characteristics of the dummy transmissions, such as duration and inter-transmission delay, are derived from the same source.

Abstract: In an electronic article surveillance system, a jamming apparatus is provided for establishing a jamming zone in which tags can be situated and not respond to message signals from a surveillance system transmitter and in which the surveillance system receiver can be situated and still respond to tag signals.

Abstract: A warning radio receiver is adapted to receive not only a recognition signal for emergency broadcast but also two further recognition signals, namely a warning network transmitter recognition signal and a warning region recognition signal. If, for example, the currently tuned transmitter changes its warning region recognition signal, after the expiration of the timing period of a first timer 16, one or more seeking operations for other transmitters with the predetermined warning region recognition signal are started. If a predetermined number of such seeking operations remain unsuccessful, the reception readiness of the transmitter is demonstrated by switchover to a transmitter associated with a different warning region. If such other transmitters also cannot be found, exceeding another predetermined number of fruitless seeking operations results in the generation of a receiver malfunction indication.

Abstract: Networks which remove the jamming signal from the television signal supplied to subscribers for a premium T.V. channel in a cable (CATV) or other subscription television system utilizes surface accoustic wave (SAW) devices arranged to provide a broadband all pass response across the entire band covered by all of the transmitted television channels except for a notch at the frequency of the jamming signal. The narrow band response of the filter in the premium channel is such that the notch presents insertion loss at the jamming signal frequency and over a frequency range to accommodate shifts in the frequency response of the SAW devices with respect to the frequency of jamming signal, which insertion loss is about 100 times the insertion loss at the picture carrier frequency of the television signal, even though the picture carrier and the jamming signal frequency may be within about 200 KHz apart from each other.

Abstract: A channel converter system includes a local oscillator for converting an input RF television channel frequency signal to an intermediate frequency and for remodulating the intermediate frequency signal to produce a channel output signal at the same frequency. Video processing is accomplished between the input converter and the output remodulator. For baseband decoding, another oscillator demodulates the intermediate frequency signal and remodulates the processed video signal to the intermediate frequency signal.

Abstract: An off-premises cable television interdiction apparatus provides a microprocessor controller for controlling and switching one or more variable frequency voltage controlled oscillators. The variable frequency oscillators selectively jam only unauthorized premium programming transmitted on particular channels of a broadband signal in the clear from a headend to a subscriber. The microprocessor controller controls the variable frequency oscillators to hop between jamming frequencies and jam particular channels under control from the headend. A frequency calibration routine is executed periodically upon power-up to determine gain parameters for the oscillators. A heterodyned variable frequency oscillator may be provided for the interdiction system which moves the frequency of the variable frequency oscillator out of the television band and mixes the variable frequency oscillator output with a fixed local oscillator output to provide a jamming signal that falls in the television band.

Abstract: A transmitter generates three signals for sequential transmission. These signals are an unmodulated r.f. carrier, an r.f. carrier amplitude modulated by a first audio frequency waveform and an r.f. carrier amplitude modulated by a second audio frequency waveform which is distinguishable from the first and which may be employed as a means for identifying a particular transmitter. The composite, sequentially transmitted signal may be varied in terms of the individual signal transmission sequence, the duration of the individual signals, overall composite signal repetition rate and the frequency of the second audio waveform. Various combinations of signal variations may be employed to transmit different information.

Abstract: This invention relates to an aircraft missile communication system comprig means to generate a digital sequence corresponding to command signals, means in the aircraft to mix the digital command sequence with the code sequence and transmit the combination to an object; means to compare the received code sequence with the second digital code sequence and means in said object depended upon the comparing means to express said digital command sequence.

Abstract: A jammer includes means for receiving a local radio transmission and means for determining the frequency of the local radio transmission. Monitoring circuits are arranged to detect the end of the local radio transmission and only then to trigger the transmission of a jamming signal by jamming signal transmitting means. In this manner the jammer jams local reception of the response of a non-local station to the detected local transmission. The jammer is able to jam effectively using a low power signal. The reduction in the power-consumption of the jammer makes it particularly suitable for use as a leave-behind jammer for military applications.

Abstract: In order to selectively jam M selected channels to selected subscribers in a CATV system, each of M different oscillating signals, each of which oscillating signals has a duration longer than the duration of the horizontal synchronization signal of the television channel it is to jam and a frequency higher than the carrier wave of the channel it is to jam, are in turn added to the television signal circuits of those subscribers who are not authorized to receive the particular channel being jammed by the jamming signal being added. The television set of the non-authorized subscriber picks up the higher frequency jamming signal as the valid horizontal synchronization signal and therefore ignores the valid horizontal synchronization signal, with the result that the channel in question is unviewable on the television set of the non-authorized subscriber.

Abstract: A stand-alone utility device for perceptible reproduction of signals, for example a radio receiver or a TV receiver, is protected from theft because the reproduction quality of the signals is disturbed in the case of unauthorized use by regular suppression of the signal, by generating bleeps or by a combination of both.

Abstract: 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.

Abstract: Off premises cable television interdiction apparatus comprises a microprocessor actuation and control means for actuating and controlling a plurality of frequency agile voltage controlled oscillators. The voltage controlled oscillators selectively jam only unauthorized premium programming transmitted in the clear from a headend to a particular subscriber. Each voltage controlled oscillator is allocated a continuous band of frequencies consistent with the elimination of jamming signal frequency harmonics which may disturb authorized programming at a higher channel frequency. The microprocessor actuation and control means provides a calibration mode and a normal mode of operation. During the normal mode of operation, a frequency hopping rate on the order of four thousand hertz is achievable.

Abstract: A Television Signal Transmission Security System which provides a higher degree of security then previously possible by utilizing encoding and decoding technology which effectively prevents pirating by amateurs or experimenters. The television signal transmitted is encoded by injecting one or more modulated interfering signals in specific frequency slots in close proximity to the video carrier. Continuous or alternating interfering signals can be injected either above or below the video carrier between harmonics of the horizontal frequencies. Combinations of interfering signals provide coding techniques making the system virtually pirate proof. The interfering signal is removed by very narrow band rejection filters having a rejection band attenuation greater than about 40 dB over a bandwidth equal to the bandwidth between adjacent harmonics of the horizontal sweep frequency. The filters are constructed using advanced technology to produce the quartz crystal bulk resonators or surface acoustic wave filters.

Abstract: An arrangement for securing data transmissions to and from one data device from among a plurality of data devices sharing a common interface is disclosed. In a data communication network, a master communication bus connects to a plurality of data transmitting and receiving devices via a single interface. The disclosed arrangement provides circuitry in the common interface which generates a jamming signal to all devices connected to the interface except for that one device which is either transmitting or receiving a data-transmission. The jamming signal inhibits all the connected devices from monitoring and detecting the data transmission processes of the interface. The one transmitting and receiving device is enabled to either transmit or receive data during the generation of the jamming signal which ensures a secure data transmission and prevents "eavesdropping" by the other devices. The jamming signal is removed at the conclusion of the data transmission to or from the one device.

Abstract: A video distribution system (e.g., CATV or MATV) employs at least one channel having a reception-defeating jamming signal which changes frequency periodically or, preferably, randomly. The signal originating head end distributes information characterizing the operative frequency of the jamming wave.At controller apparatus for authorized viewers, the jamming frequency specifying data is employed on a frequency agile basis of heterodyne the protected channel into a proper (fixed) frequency relationship with a notch band suppression filter to remove the jamming signal. The secure channel with the jamming wave removed is then again shifted to its original or other intended frequency to permit normal reception either directly by a standard television receiver, or via a frequency converter.

Abstract: A CATV scrambling system ultilizes low cost, uncritical, pole mounted components for all subscriber locations and high cost precision components only in subscriber units provided at "premium" subscriber locations. The subscriber unit includes a digital stepped oscillator for generating frequencies that are 1/10 of the frequency of the premium television signals and are supplied, along with data, to a pole unit scrambling station. The pole unit has a microprocessor which interprets the data and opens a switch for premium television signals that are to be received. The digital stepped oscillator output is supplied to a frequency multiplier which produces interfering carrier frequency signals that are injected through a directional coupler into the cable that feeds the subscriber TV/VCR. A broad band default oscillator is activated by a microprocessor in the pole unit when there is no subscriber unit or when the data is not present.

Abstract: A reception controlling apparatus for a CATV system in which jamming signals are added to the signals sent to each subscriber's terminal unit in such a manner as to accurately jam the designated nonpermitted channels without interfering with the permitted channels. A microcomputer receives data from a broadcast center indicating which subscribers are permitted to view which channels. A jamming signal is generated in a time-division manner and gated onto the lines to the individual subscribers under the control of the microcomputer. The jamming signal is produced by a VCO controlled by the microcomputer. The jamming signal is produced by a VCO controlled by the microcomputer while providing correction to its output frequency.

Abstract: Radio transmission apparatus usable for emergency vehicles transmits a radio frequency signal on both standard AM frequencies and FM broadcast frequencies to alert vehicles in the path of the emergency vehicle that the emergency vehicle is approaching. The frequencies are broadcast over the entire frequency spectrum so that vehicles using their radios will receive the signal, regardless of what particular frequency is being tuned by their receivers. A crystal controlled oscillator using frequency dividers generates carrier frequencies that are precisely on each AM and FM frequency.

Abstract: Scrambling and descrambling systems utilizing jamming signals provide improved pictures with minimal distortion due to ghosts and artifacts. The television signal is combined with a jamming signal or signals located preferably in the vestigial sideband (VSB) of the modulated picture carrier and at about a null in the spectrum of the modulation of the picture carrier by the horizontal sync. The jamming signal or signals also preferably are placed between the harmonic components of the horizontal sync which define the horizontal sync spectrum and at frequencies which comply with governmental regulations respecting frequency locations of strong signals of CATV purposes. The jamming signals are generated by phase locking to the horizontal sync signals of the television signals or to a submultiple of the horizontal sync frequency.

Abstract: A security system having one or more sending units for transmitting an electromagnetic signal representative of a condition such as fire, smoke, intrusion, battery condition, an emergency or other condition to a central receiving unit. Upon reception of an electromagnetic signal, the receiving unit provides an electromagnetic carrier detect signal to a microprocessor. A software timer within the microprocessor keeps track of the time over which the carrier is detected. If the carrier detection continues for a time longer than about 20 seconds, then a jamming indication signal is provided to one or more outputs. While the system is being jammed, alarms are ignored thus avoiding false alarms due to interference.

Abstract: An electronic device for rapidly tuning a voltage controlled oscillator to the radar carrier frequency of each of the individual radar pulses. A frequency discriminator (1) of the quadricorrelator type is supplied with the incoming pulses and with the output of the VCO (5) to provide the control voltage to the VCO (5) via amplifying stages (2), (4) and a sample-and-hold circuit (3) that maintains the tuned frequency for time durations greater than 100 usec. The operating frequency range of the device is between 6GHz-18GHz.

Abstract: A pseudorandom noise generator (10) is disclosed which includes a maximum length sequence generator (13) for providing a digital signal having a pseudorandom sequence, modulating circuitry (17,20, 25, 27, 33) responsive to the digital signal for providing a constantly changing modulation signal which changes linearly. In one embodiment, the modulation circuitry provides a sequence of linear ramps which remain within predetermined limits, and a voltage controlled oscillator (29) responsive to the modulation signal for providing a pseudorandom noise output VCOUT. The modulating circuitry causes inversion of the slope of the ramps when they reach the predetermined limits.

Abstract: Antenna and processing provisions for the suppression of mutual interference between flying bodies used for jamming radio/radar transmitting and receiving systems. A transmitting and receiving device is contained within the flying body for generating jamming signals in dependence of received signals. A transmitting and receiving antenna arrangement is installed on the flying body and connected to the transmitting and receiving device for producing a plurality of directional and linearly polarized electromagnetic radiation patterns covering respective azimuthal sectors, the patterns each having a major beam direction and a polarization plane which has a 45.degree. inclination with respect to a horizontal reference plane when the flying body is in the normal flight attitude, the inclination with respect to the horizontal plane being in the same direction for all of the patterns with respect to the respective major beam direction as viewed from said flying body.

Abstract: An antenna system for a flying body for jamming radio/radar signal transmitting and receiving devices. The antenna system includes a receiver with a frequency discriminator, a transmitter with a variable frequency oscillator, a transmit/receive device for conducting signals to the receiver and for conducting the transmitter signal to the antennas, a switch for selectively or cyclically connecting the antennas to the receiver and transmitter, a time which enables the receiver device to receive signals from antennas during one complete cycle of the switch and which enables the transmitter during the subsequent transmit mode to furnish transmitter signals to selected antennas for at least one complete cycle of the switch and a memory in which frequency representations are stored so that each representation corresponds to a particular antenna via which signals were received.

Abstract: A jamming circuit for a CATV system in which the jamming signal is offset in frequency by a voltage controlled oscillator and then mixed with the unjammed television signal. A difference component is obtained from the mixer and is attenuated to a fixed level. This signal is then 100%-AM-modulated by a low frequency signal. The AM-modulated signal is mixed with an output from the voltage controlled oscillator and the double side bands are superimposed on the television line feeding the terminal of the subscriber.

Abstract: A pseudorandom noise generator which operates in different modes is disclosed. The pseudorandom noise generator (10) includes circuitry (11,13) for providing a digital signal having a pseudorandom sequence at a selected clock rate; a modulation control circuit (15, 17, 20, 23) for selectively providing a modulation control signal that corresponds to either a non-filtered or filtered version of the digital signal, and for controlling the mode of operation of the noise generator; a modulation circuit (27, 29, 31, 33) responsive to the modulation control signal for providing a modulation signal; and a voltage controlled oscillator (VCO) (35) responsive to the modulation signal for providing a VCO output having a relatively constant output spectrum and high spectral containment for each mode of operation pursuant to control by the modulation control circuit and the modulation circuit.

Abstract: A portable low-output-level generator producing simultaneous audio, ultrasonic and RF noise for the test and demonstration of instruments designed to locate electrical interference, for demonstration of the broad frequency spectrum of electrical noise radiation, for antenna tests, to test the EMI susceptibility of electronic equipment, and to illustrate the effects of said noise on TV and radio receivers. This generator is enclosed in a housing and communicates audio and ultrasonic sounds to the observer via a vibrating diaphragm mounted on the face of the housing, with means provided to attenuate the audio sounds relative to the ultrasonic, and this generator radiates RF from a retractable antenna mounted on and extending outward from the housing.

Abstract: In an anti-theft apparatus for vehicles with wireless transmission of the code signal, the latter is suitably overlapped outside of the vehicle by a secondary signal which is not to be received in or on the vehicle. This results in an effective protection against interception of the code signal.