Abstract: A two-channel audio amplifier for use in a vehicle sound system is provided. Each channel drives a pair of loudspeakers and includes a common amplifier connected to drive one terminal of each speaker. The remaining speaker terminals are connected to the outputs of a pair of additional amplifiers. Signals of one phase are applied to the common amplifier. Signals of opposite phase are applied to the additional amplifiers. Signals in phase with the common amplifier are applied to the inputs of the additional amplifiers through field-effect transistors. Control signals applied to the control electrodes of the transistors control the magnitude of the applied in-phase signal to independently control the output level of the speakers.

Abstract: A single carrier is amplitude-modulated by a signal which is a transform (as the sine function) of the audio signal, and one set of sidebands is removed. In a receiver, the signal can be recovered by first deriving the Hilbert transform of the sine transform, and multiplying it by the signum of the derivative of the original audio signal to obtain the cosine transform. The sine and cosine transforms are then decoded to obtain the original audio signal.

Abstract: A single alternator having multiple isolated windings provides multiple outputs as for charging 12 and 24 volt batteries. A main regulator controls the field coil current and a secondary regulator controls the charging current for the second battery by controlling the second rectifier.

Abstract: An internally generated raster scanning circuit includes self correction for pincushion distortion by multiplying the horizontal parabolic wave form by the vertical saw-tooth wave form. The multiplier is biased to provide the required 180.degree. phase shift at the midpoint of the waveform. The multiplied signals are coupled back to an input of the existing power amplifier and a corrected current is then supplied to the vertical yoke coil, requiring no added reactor transformer. The balance or ratio of the top and bottom correction currents can be adjusted as required by a simple control in the multiplier circuit.

Abstract: In the field of AM stereo detection, co-channel or adjacent channel interference may cause some distortion and side-to-side movement of a stereo signal source as well as false "stereo detect" signals in AM stereo receivers having phase locked loop (PLL) systems. The invention provides a filter receiving the incoming signal and passing only the frequencies resulting from said interference; a sensor measures the output of the filters and if this signal is above a given level, the monophonic mode is enabled, i.e., the pilot detector, the stereo presence indicator and the stereo mode switch are disenabled for a timed interval. A higher given level of interference is required for stereo disenablement when stereo transmission with pilot tone is already being received.

Abstract: The volume of gases in a container or the volume of liquid in the container is determined by creating cyclic pressure waves in the gases and detecting the waves by a second transducer. The signals produced by the second transducer are a function of the volume of gas in the container, and the volume of any liquid can be obtained by simple calculation. The signals can also provide detection of an open container and, when coupled to signals relating to the velocity of a vehicle, can provide other data such as a miles-per-gallon reading.

Abstract: A battery charging device wherein the charging current level is controllable by a thermal circuit responsive to battery temperature also includes a circuit responsive to battery voltage and a timing circuit. The timing circuit is activated when a battery is inserted into the device for charging and immediately times a very brief interval. If the battery voltage exceeds a predetermined level during the timed interval, the charging current level is reduced as by the thermal circuit. The circuit protects both cold and charged batteries from damage due to overcharging.

Abstract: A circuit providing a known change in a parameter of a function without interfering with the basic operation of the function is utilized in an audio circuit "loudness contour" control. Bass and treble controls function independently of the volume setting while desired contours are obtained at each volume control setting.

Abstract: A semi-duplex communication system provides high channel efficiency by having the base station transmit a reference signal which each terminal uses as a sync signal. Each unit having data to send to the base responds with a very brief signal such as a burst of silent carrier transmission during an assigned time slot in a queue of slots. Only those units which responded thus are polled during the subsequent polling cycle. During the transmission time slots, the base can be sending acknowledgments to those terminal units having sent messages during the previous polling cycle. While polling for data or acknowledgments or sending acknowledgments, the base can also be listening for the respective responses. The address code of a terminal unit is further encoded to carry other required information in both directions.

Abstract: A CRT in a CRT device is degaussed following a timed period of device inactivity and while the screen of the CRT is darkened, as well as at device turn-on or at manual activation. The screen stays darkened until data is inputted, and degaussing reoccurs during each subsequent timed period of inactivity.

Abstract: A remote unit can be controlled by sensing the change of impedance in the power line of a control unit as the control unit is turned on. The power line circuit includes a portion of an oscillator which is damped by the turn-on. Functions such as power turn-on and temporary audio muting are possible with minimal voltage drop in the power line.

Abstract: A horizontal oscillator for a CRT device runs at a rate higher than the line rate, and has a wide lock-in range. The horizontal sync signal is delayed in an adjustable monostable circuit and coupled to the oscillator for allowing a centering adjustment of one full line. The oscillator output signal is coupled through a discharge circuit for rapid discharge of the subsequent circuit in the CRT device as desired.

Abstract: One circuit, providing a feedback signal from the horizontal output transistor to the horizontal drive circuit, prevents damage to the output transistor in the event of a disruption or noise in the input signal, and also prevents "spot burn" of the CRT screen if the input signal should fail while there is still a charge on the CRT.

Abstract: A low frequency tone detector filters out undesired frequencies in a received signal, than a latching circuit locks on when a given number of low frequency cycles are detected, having at least a predetermined peak amplitude. Thereafter, only a second given number of missing or low amplitude cycles will reset the latch. When the detector determines that the received signal is weak or of very poor quality, false detect signals are essentially prevented. The circuit is particularly suited to use with AM stereophonic signals where a low frequency tone is added to the difference channel for providing mono/stereo indication and mode switching.

Abstract: A low frequency tone detector filters out higher frequencies, then a latching circuit locks on when a given number of low frequency cycles are detected which have at least a predetermined peak amplitude. Thereafter, only a second given number of missing or low amplitude cycles will reset the latch. The circuit is particularly suited to use with AM stereophonic signals where a low frequency tone is added to the difference channel for providing mono/stereo indication and mode switching. The circuit can also provide an early detect for use by a scanning circuit in a receiver.

Abstract: Sensor inputs as from an engine load sensor alter the frequency of a pulse providing circuit, the output of which adds counts to those counts provided as a function of engine velocity. The total number of counts is used for determining the instantaneous advance angle in a distributorless ignition system.

Abstract: Field coil current of an alternator is controlled in response to temperature as well as to battery voltage, thus allowing maximum safe output power at any ambient temperature. A monostable circuit is utilized for reducing the maximum duty cycle of the field excitation driver in response to a sensed temperature without increasing power dissipation in the regulator.

Abstract: The circuit determines which cylinder is to be fired and continually updates the determination so that the circuit recovers immediately from any false detect and responds to any change of engine condition. The dwell timing is derived from sensors adjacent the flywheel and, to achieve the widest possible range of advance angles, the use of certain sensor-derived signals is delayed until after spark.

Abstract: Logic circuitry in a portable electronic device is combined with the microprocessor to reduce power consumption in the microprocessor and its associated memories during inactive periods of the device, with periodic sampling for inputs from peripherals or received data which would require active operation of the device.

Abstract: The circuit determines whether an incoming frequency is within the normal "lock-in" range of a phase locked loop VCO or not, and whether it is higher or lower than the VCO frequency. If not within normal range, the beats are rectified and gated to provide a DC control voltage of the proper value and polarity for locking the oscillator on the incoming frequency. Rectification may be half or full wave as needed, and the circuit may include filter bandwidth control as well. This circuit is suitable for signals of any waveform, quadrature signals, and AM stereophonic signals.