Abstract: Mileage tracking devices track a vehicle's mileage. A top is hingedly attached to a bottom in a “clamshell” design. The front of the top has an LCD touchscreen, and the front of the bottom has a keypad. The rear of the top has a solar panel, and the rear of the bottom has a battery compartment enclosing a rechargeable battery. One side of the bottom has a USB port, and the opposing side of the bottom has a power port that receives one end of a car charger. Voice recognition software and data are stored in memory accessed by a microprocessor. The mileage tracking device provides calculator, calendar, address book, mileage log, and car maintenance functions. The LCD touchscreen displays the current date and time and the level of charge of the rechargeable battery.

Abstract: In a television receiver the voltage applied to the loudspeaker from the audio amplifier is low pass filtered and coupled to a threshold detector. Normal audio is attenuated so that the detector is not tripped, but steady DC is passed through the filter and trips the detector. The output of the detector is coupled to the X-ray protection circuit of the receiver which acts to shut the receiver "off".

Abstract: A protection circuit for an audio output channel of a television receiver includes a detector which detects the presence of either or both of (1) a sustained DC component applied to the loudspeaker form the audio power amplifier, (2) and the loss of a supply voltage for the power amplifier. The presence of a of a sustained DC component can damage the loudspeaker. The loss of a supply voltage of the power amplifier can damage the power amplifier and can also result in the application of a sustained DC amplifier and can also result in the application of a sustained DC component to the loudspeaker. For example, the loss of the negative supply voltage of a power amplifier incorporated in an integrated circuit results in the removal of potential from the substrate which otherwise serves to electrically isolates various semiconductor devices supported by the substrate.

Abstract: A stereo expansion circuit has right and left amplifying channels for providing expanded stereo signals. A selection device comprises a switch cross coupling the signal channels for providing expanded stereo when the switch is closed. Circuitry is provided for preventing the switching control signal from being coupled to the signal channels. More specifically, a version of a signal coupled between the signal channels through the conduction channel of the switch is applied to the control input of the switch to inhibit the control signal from being coupled to the conduction channel. Such an arrangement is particularly advantageous when the switch comprises a J-FET.

Abstract: Apparatus is provided for the virtual expansion of the power providing capacity of a power supply, e.g., for a stereophonic audio system with a given number of channels which may be selectively increased to provide a surround audio system. A plurality of amplifiers, each having an adjustable gain, are powered from the power supply. The current drawn from the power supply is sensed. When additional amplifiers are activated, the total amount of power drawn by all of the amplifiers can exceed a predetermined level which corresponds to the original plurality of amplifiers. However, when it is sensed that the total amount of power drawn exceeds the predetermined level, the gain of all of the amplifiers is reduced so that the power drawn from the power supply does not exceed the predetermined level. Thus, the virtual power providing capacity of the power supply is expanded to power the additional amplifiers.

Abstract: An oscillator includes a mechanical resonator, such as a crystal, and having an amplifier arranged for oscillating at a first frequency. A resonant circuit is coupled in series with the crystal. The resonant circuit is antiresonant at an undesired harmonic frequency of the crystal thus prohibiting oscillation of the oscillator at said undesired harmonic frequency. The present oscillator is a portion of a phase locked loop used in a television receiver for demodulating a composite stereophonic audio signal.

Abstract: In a television receiver apparatus is provided for muting an audio power amplifier having continuous operating supply voltage applied thereto from a standby power supply even when the receiver is in an "off" condition so that spurious noise and hum coupled to the power amplifier will not be amplified and heard by the viewer. The muting is applied via a microprocessor controller which controls and senses the power supply status of the receiver as well as mutes the power amplifier in both the "off" and the "on" conditions.

Abstract: A stereo expansion circuit selection switch includes a transmission gate to cross couple the right and left channels as needed for stereo expansion.