Abstract: Disclosed is an essentially on-chip switching power supply circuit for generating from a single 5 volt power supply high positive and/or low negative voltages of the order of .+-.25 or more. The circuit consists of a pulse generator which alternately activates a positive rail voltage circuit and a negative rail voltage circuit. The positive/negative rail voltage circuit consists of a positive/negative electronic switch in series with a positive/negative voltage generator having an output terminal where the required positive/negative voltage output is generated. The positive/negative voltage generator consists of an inductor and output capacitor coupled together via a rectifying diode.

Abstract: An alarm pull station is provided having a housing for attachment to a support, a manually movable member mounted within the housing and having a magnet attached thereto, and a Hall effect switching device responsive to movement of the magnet for providing an output signal. The Hall effect switching device can include first and second Hall effect sensors arranged for providing three levels of output signal, a first normal level when the manually movable member is in its original, unoperated position, an alarm level when the manually movable member is operated, and a trouble level when the pull station is subject to tampering.