Zenith Radio Corporation

Judson A Hofmann

Paul A Snopko

A television receiver comprises a television system energized by the powerlines of a commercial power grid, a telephone network access system including a microphone disposed in close proximity with the audio speaker of the television system and a remote control system enabling the receiver to be operated in a television mode or a telephone mode. The television receiver according to the invention is characterized by having an annunciator/intercom enabled for operation by the remote control system. In the annunciator mode, the audio section of the television system is disabled and the microphone is connected through a radio-frequency signal transmitter to the power lines for generating a radio-frequency signal for local transmission. A frequency-modulator is included for modulating the radio frequency signal. At least one remotely located radio-frequency receiver coupled to the power lines is provided for receiving and demodulating the radio-frequency signal and rendering audible television receiver user voice signals. The television receiver user can therefore announce a telephone caller when the television receiver is operated in the annunciator mode. Alternately, intercom units may be employed to provide a two-way intercom conversation link between the television receiver user and a remotely located called party.

Television/telephone system with annunciator and intercom feature

A detector is described for fully rectifying a low level A.C. input signal without developing switching transients or substantial levels of undesirable signal components. The output of the detector is substantially equal to the square root of the sum of the square of the input signal and the square of a bias component. To remove the bias component, a linearity enhancer is described which receives the output of the detector and develops a further output substantially equal to the square root of the square of the A.C. input signal. The linearity enhancer may also be employed without the detector to remove undesired component from a signal which can be represented as the square root of a polynomial.

Full wave rectifier envelope detector

A television receiver has a tuner, an intermediate frequency amplifier, and a detector for recovering a composite signal including horizontal and vertical display synchronization components and picture information. Horizontal display means produce a long-duration trace signal and short-duration retrace signal and a coincidence gated AGC system which is responsive to coincidence of the horizontal retrace signal and horizontal synchronization signal controls the gain of the intermediate frequency amplifier. A combination synchronizing signal separation and AGC lock-out defeat circuit comprises a transistor, having an input electrode DC coupled to the detector, a common electrode coupled to a charge-discharge circuit such that the input-to-common electrode junction of the transistor and the charge-discharge circuit cooperate to establish a bias voltage dependent upon the occurrence and amplitude of the display synchronization signals, and an output electrode DC coupled to the AGC system. An override system response to said bias means overcomes the coincidence requirement of the AGC system to render said AGC operative solely in response to the occurrence of horizontal retrace signals when the bias indicates prolonged absence of sync pulse signals.

Television synchronizing signal separating circuit

A television receiver includes conventional circuitry for receiving processing and detecting an information bearing signal. Vertical scansion means respond to recovered synchronizing information and provide vertical scansion of a conventional cathode ray tube. A horizontal oscillator coupled to an output amplifier and high voltage generator generates a scansion signal and provides horizontal scansion of the cathode ray tube. An automatic phase control loop (APC) includes a differential amplifier phase detector which responds to the reference sync pulses and the horizontal output signal to produce an error voltage which is stored in a hold capacitor. A speed control amplifier coupled to the receiver AGC system varies the amount of phase detector action directly with signal strength to vary system speed.

Variable speed horizontal automatic phase control

A frequency scanning automatic phase control includes a phase detector, a local oscillator and an APC filter. A coincidence detector includes an AND gate responsive to the horizontal retrace and reference synchronizing pulses. A lock detector also responsive to the retrace and reference sync pulses produces an output signal when a predetermined interval of non-coincidence has existed. An AND gate responsive to both the lock detector and coincidence detector gates a current sink which unbalances the phase detector producing a ramp-like error voltage across the APC filter. A threshold detector coupled to the APC filter activates a discharge circuit also coupled to the filter when the filter voltage exceeds the threshold. The oscillator responds to the variations of error voltage and changes frequency accordingly. Once coincidence occurs frequency variation ceases and is resumed only if non-coincidence returns.

Frequency scanning automatic phase control system

An additional signal is supplied to an integrated circuit, including a voltage regulator and a plurality of electronic circuit elements, by impressing the signal on a terminal coupled to the voltage regulator. Circuitry in the integrated circuit recover the signal by detecting the voltage regulator response thereto. Method and apparatus with voltage regulators of shunt and series type are described.

Growing community of inventors

Schaumburg, IL, United States of America

Judson A Hofmann