Abstract: A valve actuator for use in a pressure regulator. It comprises an electromagnetic having a plurality of pole pieces. A valve actuating permanent magnet is moveably secured to one of the pole pieces. The pole pieces are so disposed relative to each other that four distinct magnetic forces combine to urge the permanent magnet in a first or second direction depending on the polarity of current applied to a coil disposed about one of said pole pieces.

Abstract: A photo sensor circuit including an LED (12) and a phototransistor (14) coupled together by resistors (R.sub.1, R.sub.2) and connected to a drive and sense network (16) including resistors (R.sub.B, R.sub.3, R.sub.4), a source of positive voltage (+Vcc) and a PNP transistor (20) by a single conductor wire (W.sub.1). When the light path between the LED (12) and the phototransistor (14) is blocked, the circuit standby current is low and the transistor (20) is OFF, but when the light blockage is removed, the increase in current through the LED (12), triggered by an increase in current through the phototransistor (14) quickly drives the transistor (20) into saturation. The phototransistor (14) will keep full current flowing through the LED (12) as long as the light blockage is removed.