Abstract: A compact and economical circuit for a multitone horn employing a microcomputer. The system also includes an audio amplifier, a speaker, a power supply, and start control means. The start control means includes a common lead and a plurality of star leads. Connecting the common lead to a predetermined one of the start leads will initiate a predetermined one of the plurality of available tones. A selected one of the start leads may have priority to terminate any pre-existing signal and initiate an alternate signal. At least one of the start leads, including the priority start lead, may be coupled to programming means whereby the signal activated may be preprogrammed to be any selected one of the plurality of available signals. The power supply includes a pulse generator for resetting the microcomputer in response to initial application of power. The available tones include both percussive and non-percussive tones and the total number of available tones may be greater than the number of start leads.

Abstract: A smoke detector of superior smoke sensitivity characterized by a compact unipolar ionization chamber in which the ionization area or zone is situated and defined between the source of alpha particles and an electrode which confronts the source; another electrode, which attracts the unipolar charge carriers, is situated on an indirect path from the source, preferably being behind such source with respect to the pattern of radiation emitted therefrom.

Abstract: A ground fault current detection and disconnect device. A differential current sensing transformer is employed together with a second transformer having one winding in series with the neutral conductor and another winding serving as an auto-transformer with a part thereof coupled across the line and netural conductors. The auto-transformer provides an alternating current power supply to a diode bridge, the output of which provides a direct current power supply for an operational amplifier. The output of the sensing winding of the differential transformer is an input to the operational amplifier. When the output of the operational amplifier exceeds a predetermined level, an SCR is triggerred on and a circuit disconnect device, bridged across the line and neutral conductors in series with the anode and cathode of the SCR, opens the power supply to the load. Circuit elements are provided to limit the effects of surge currents and line disturbances.