Abstract: A flush-mount swivel tweeter system for vehicular audio utilizes a tweeter unit enclosed in hemispherical shell housing, which fits in a swivel manner into a mating cavity in a mounting bushing configured externally with a threaded sleeve having a thin peripheral decorative front flange. The resulting swivel tweeter assembly can be flush-mounted through a round opening provided in the host panel. The flange is secured against the panel by a large mounting nut threaded onto the mounting bushing from the rear. A circular aiming range is available by a combination of swivelling the tweeter unit off-axis and rotating the entire assembly in the panel opening. Once aimed, the swivel tweeter is clamped in place by a nut and washer at the rear, and the mounting bushing is secured in place by tightening the large mounting nut against the rear of the panel.

Abstract: An improved digital switching amplifier is disclosed. The amplifier utilizes a low-pass filter at the input of the switching comparator to give an improved signal to noise ratio at the final output. In another aspect of the invention, a propagation delay is used to produce the steady-state oscillation of the amplifier circuit.

Abstract: An amplifier housing assembly particularly useful for automobile stereo systems is disclosed. The assembly comprises a mounting plate which bolts to a stationary surface and an amplifier enclosure which mounts on the mounting plate. Wires from speakers and a power source are connected to the mounting plate which are then connected to the amplifier when the amplifier housing is mounted on the mounting plate by means of male and female connectors. An antitheft feature of the housing is that the mounting bolts of the mounting plate are rendered inaccessible when amplifier enclosure is mounted on the mounting plate.