Abstract: The device includes a housing containing a dc battery, a microphone, an audio tone signal source, and a speaker and headphone jack which can receive audio signals from either the microphone or the tone signal source, and two multi-pin XLR receptacles or jacks, one of which is male and the other of which is female. The connectors can supply audio signals from the microphone or tone signal source to the input of the speaker and headphone jack, or alternatively, such signals can be outputted by the male connector to a circuit external of the housing, or a source external to the housing can be utilized to supply audio signals via the male or female connector to the speaker. Power from the battery is supplied selectively either to the microphone or to the tone signal source by a switch which can be moved to either of two different operative positions, or by a volume control knob which applies power to the speaker circuits.

Abstract: The device includes an audio signal circuit having two separate terminals that are connected through the photoresistor elements of two, separate, optical isolators with an audio signal input/output terminal, so that signals can be routed selectively and bidirectionally along separate signal paths to or from the input/output terminal to one or both of the two separate terminals. A separate control circuit supplies DC power selectively to the LED's which control the selective energization of the photoresistor elements of the optical isolators, the advantage being that the photoresistive devices permit selective blocking of the audio signal paths without physically opening or interrupting the paths and thus avoiding objectionable signal spikes and consequent loud popping sounds in associated loud speaker systems. The DC control circuit includes two, manually operable double pole, double throw switches for controlling the selective routing of signals between the audio signal terminals.

Abstract: A generally tubular plastic collet, which is mounted coaxially in the bore of a rigid, tubular housing, has on one end thereof a plurality of radially flexible jaws that surround one end of an electrical cord that extends into the housing bore at one end thereof. A metal tip has an externally threaded shank that is adjustably threaded into the opposite end of the housing bore, and an elongate stem portion which projects to the exterior of the housing. The tip comprises a pair of coaxially disposed conductors insulated from each other in a conventional manner, and connected in the housing to a pair of wire conductors that project from the cord. The threaded end of the tip engages and urges the collet axially toward the inlet end of the housing, thereby flexing the collet jaws radially inwardly into gripping engagement with the cord.