Abstract: The assembly comprises a light-emitting diode (28) and associated circuit components (38, R1-R4) mounted on a printed circuit board (26) all mounted within a housing (10) formed with securement means such as a screw thread (14) for mounting the assembly in a panel (18) with the led (28) visible from the opposite side of the panel. The circuit components form means for converting a mains voltage at input leads (30) to a low voltage for driving the led, preferably in the form of an i.c. rectifier bridge (38) and a plurality of volgage-dropping resistors (R1-R4).

Abstract: A proximity-switch circuit operates a main switch TH1 to pass an ac supply through an external load when a metallic object is near a coil L1 that is part of an oscillator circuit. The oscillator circuit is connected to a level detector circuit controlling the switch TH1. The circuit is powered by a power supply stage that includes a storage capacitor C7, for which the charging current is controlled by a transistor T10 and a MOSFET T11. Upon initial application of the ac supply, the level-detector circuit is overridden by a circuit that includes capacitor C3 and transistor T4 until a predetermined period of time has elapsed, so as to prevent the generation of erroneous "on" signals before the oscillator has stabilized.

Abstract: The circuit operates a main switch SCR to pass an a.c. supply V through a load L when a metallic object is in proximity to coil L1. Coil L1 is driven by an oscillator comprising transistor T2 and associated components. SCR is gated on simultaneous occurrence of an output from level detector T3 and a signal from T5, these being ANDed by T4. The timing of the signal from T5 in the supply cycle is governed by the RC time constant of C4,Z1,R14 and is such that the power supplied to the oscillator and level detector is the minimum necessary, for a wide range of supply voltage and load current.

Abstract: The switch is of the type, known per se, in which an induction coil is driven by an oscillator. The coil is initially positioned in an end cap and secured therein by potting with epoxy resin. This allows the coil and cap to be handled as a unit during manufacture without damage to the coil. The switch is calibrated and adjusted automatically by abrading away part of a resistive layer on a circuit substrate. The circuitry of the switch has its lower potential side coupled to the housing via a capacitor, by means of a conductive adhesive tape trapped between the housing and an end closure.