Abstract: A signal presence detection method for use in systems where a multiplicity of types of noise is expected, wherein the spectral characteristics of the input wave is compared with corresponding characteristics of the expected noise wave and wherein the determination that signal is present is made only if the input wave mismatches all of the compared noise waves' spectral characteristics. Another embodiment of the invention compares the waveshape of the input wave and the noise waveshape.As a result of this procedure, a sensitive signal presence indication is obtained which is relatively immune to noise level.

Abstract: A system for use with equipment designed for transmitting a relatively wideband signal over two or more relatively narrowband circuits so as to provide good overall system reliability even though the relability of the individual narrowband circuits is poor.

Abstract: The false alarm rate of security systems is reduced by utilizing information generated immediately prior to the activation of alarm means. This information is stored in recording means such as a magnetic tape recorder. The recorded information may be later transmitted to a remote site to help in judging the validity of an alarm.

Abstract: A transmitter for an independent sideband (ISB) AM stereo system is provided with a phase modulator which includes means for generating second order upper and lower sidebands which are proportional to the stereo difference signal. No second order upper and lower sidebands are generated when the L and R audio signals are equal. The phase modulator uses an ISB suppressed carrier signal generator and a quadrature demodulator which demodulates the quadrature component of the output of the ISB generator. This demodulated component is used in a balanced modulator to modulate the ISB signal and thereby generate a signal having a carrier and upper and lower first and second order sidebands. This signal is combined with a carrier signal of selected amplitude and the ISB suppressed carrier signal to provide an output signal which, after limiting, is a phase-modulated signal having first and second order upper and lower sidebands. When the L and R signals are equal, all of the sidebands of this signal vanish.

Abstract: An improved system and method for reducing adjacent channel interference in radio systems by making use of the so called "cocktail party effect". Also, the selectivity is improved by measuring the level of adjacent channel interference above and below the desired channel and automatically changing selectivity characteristics of the receiver in accordance with the measured interference.The system is particularly applicable to the reception of AM Stereo signals but it may also be used to improve the performance of monophonic systems.

Abstract: A system and method for improving the spectrum utilization of voice communications channels by increasing the number of voice conversations a given number of lines can service. This invention can be used to improve the reliability and efficiency of conventional TASI (Time Assignment Speech Interpolation) systems and allow such systems to provide good performance when utilizing a mixture of types of telephone lines; including, microwave, cable, and satellite, and two wire configuration lines.

Abstract: A system and method for improving the spectrum utilization of voice communications channels by increasing the number of voice conversations a given number of lines can service. This invention can be used to improve the reliability and efficiency of conventional TASI (Time Assignment Speech Interpolation) systems and allow such systems to provide good performance when utilizing a mixture of types of telephone lines; including, microwave, cable, satellite, and two wire configuration lines.

Abstract: A method and means for compensating for the limited bandwidth of antennas and antenna coupling networks and other high powered modulated wave equipment characterized by generating a modulated wave at a relatively low power level, passing the modulated wave through circuitry which imparts the required envelope and phase modulation to the modulated wave to compensate for said limited bandwidth characteristics and then amplifying the resulting wave in amplifiers which substantially maintain the said imparted envelope and phase modulation and which feed the limited bandwidth equipment.

Abstract: An improved system and method for reducing adjacent channel interference radio systems by making use of the so called "cocktail party effect". Also, the selectivity is improved by measuring the level of adjacent channel interference above and below the desired channel and automatically changing selectivity characteristics of the receiver in accordance with the measured interference.The system is particularly applicable to the reception of AM Stereo signals but it may also be used to improve the performance of monophonic systems.

Abstract: An improved system and method for processing and amplifying double-sideband suppressed or reduced carrier waves using high efficiency amplifiers and not requiring frequency dividers. Typical practice of the invention involves generating a double-sideband suppressed carrier wave in a balanced modulator; for example, at a sub-harmonic carrier frequency and multiplying the frequency of the output of the balanced modulator by an odd multiplication factor greater than one in the modulated amplifier.The required envelope modulation (amplitude modulation) component is derived from the original balanced modulator output by use of an envelope demodulator and the component is used to modulate the modulated stage so as to reproduce the double-sideband suppressed carrier wave at a high power level.This invention may also be used in reduced carrier double-sideband transmitters; i.e.

Abstract: A security system for use in homes, hotels, businesses, schools, streets, and other locations requiring a high degree of security but where it is important to insure the privacy of the protected individual.

Abstract: A squelch circuit for muting constant amplitude interference when the signal is absent. The input wave's envelope characteristic is examined so as to determine if the envelope is constant and, if it is, a gate is controlled so that the input wave is muted. Time delay circuitry is provided in one embodiment in order to provide sufficient time to make a determination that constant amplitude interference is present rather than variable amplitude speech before muting the input wave.

Abstract: A system and method for improving the spectrum utilization of communications channels.In certain embodiments of the invention a plurality of narrowband communications channels are used to transmit a multiplicity of speech signals.In another embodiment of this invention, a multiplicity of speech signals jointly utilize a common transmission facility and circuitry shifts the amount of bandwidth assigned to each channel as a function of the short term characteristics of the individual speech signal.Special circuitry is provided to reduce the loss of consonant sounds at the initiation of speech bursts as well as the end of the bursts.

Abstract: Means and method of reducing the probability of false indications of microphone activity in a multimicrophone system incorporating means for sensing the activity of microphones.The microphone, which is truly active, will receive its signal from its user before any of the other microphones receive the signal. The microphone circuit then sends a control wave to all of the other microphone channels reducing their amplifier's sensitivity and making them insensitive to false indication of activity.

Abstract: Compatible AM stereophonic receivers for reception of a radiant energy carrier wave modulated with two stereo related signals (L and R), each appearing as a respective first order single-sideband. Receivers embodying the invention in general improve an optimize output stereo signal quality by quadrature demodulation of the carrier to derive the stereo difference (L-R) signal, together with in-phase detection of the stereo summation (L+R) signal, the L+R and L-R signals thus derived being placed in phase and combined through sum and difference circuits to obtain the stereo related (L and R) outputs. Demodulation distortion may be minimized by inverse amplitude modulation of the carrier wave with a portion of at least the envelope fundamental (and preferably also one or more harmonics thereof). The carrier wave is preferably enhanced prior to quadrature demodulation and preferably is also modulated with an infrasonic frequency (e.g.

Abstract: An improved system and method for protecting communications systems using in-band signaling from malfunction which may produce serious circuit failures such as false operation of the disconnect circuit.Typical practice of the invention involves detection of those main signal sounds that are similar to and imitate the in-band control tones and using the detected sounds to control a switching circuit which inserts a band reject filter into the system so as to reduce the amplitude of such sounds before they are fed to the communication system utilizing in-band signaling.Under normal conditions such sounds are not present or are of insufficient amplitude or are present for too short a time period to cause false operation. Accordingly, the band reject filter is not normally active and there is no degradation of frequency response.

Abstract: A circuit is described for operating on a carrier wave in a transmission signal including a reduced carrier with a single sideband. The carrier wave is isolated, limited, divided in frequency by a predetermined amount, and then restricted in frequency by a band pass filter. The output of the band pass filter is then multiplied in frequency. After this, the carrier wave is mixed with the sideband frequencies and the signal is demodulated.

Abstract: Compatible single sideband (CSSB) transmission system utilizing a three tone generator to develop the characteristic CSSB modulation of an electromagnetic energy carrier wave, i.e. a somewhat reduced level carrier, a full level single sideband, and a lower level second order sideband, with only nominal envelope distortion and within the narrow bandwidth restrictions commonly assigned to voice communication systems and the like. In one aspect, the invention accomplishes restriction of the bandwidth of the transmitted CSSB signal by conjunctively or alternatively using only the relatively low audio frequencies (frequencies below about one-half of the frequency span of the prescribed bandwidth) to modulate the CSSB generator and separately modulating a single sideband suppressed carrier (SSBSC) generator with the higher audio frequencies, then summating the respective generator outputs to provide the transmitted signal.

Abstract: Amplitude modulation (AM) stereophonic transmission receivers for reception of a radiant energy carrier wave with two stereo related signals, each appearing as a first order single-sideband, the carrier wave preferably being also modulated with an infrasonic frequency (e.g. 15 Hz) signal indicating stereo signal presence (with such infrasonic frequency modulation being either amplitude modulated or phase modulated). The upper sideband and the lower sideband portions of the received signal are separately detected and through voltage comparison means are applied to the development of automatic switching control of the detector outputs to deliver as receiver outputs either stereophonically related audio signals in the presence of different upper and lower sideband detector outputs or to deliver monophonically related (i.e. combined) detector outputs in the instance of reception of a monophonically modulated carrier wave.

Abstract: A system for illuminating the display of a wrist watch by motion of the wrist. The watch incorporates means for sensing a specific motion of the watch and the sensing means is connected to means to cause the digital display to become active (illuminated).Storage means is provided for illuminating the display for a 5 second interval so that the user may conveniently read the display. Additional circuitry for displaying the day and month is described.