Electrical wiring accessory with indicator lamp

A mains wiring accessory comprising an indicator lamp 14 provided with an isolator 16 operable to block applied Direct Current (DC) Voltage from causing a current to flow through the indicator lamp. The isolator and indicator lamp may be connected between a switched live conductor 18 and a neutral conductor 20. The isolator may be a high-pass filter which allows DC resistance testing of the mains wiring accessory, such as testing the insulation performance. The high pass filter may comprise a series capacitor (C, figure 2). The high-pass filter may be replaced by other types of isolator, such as an electrically operated mechanical switch- a relay, or a low-pass filter. The indicator lamp may be a neon bulb or an LED. The isolator allows AC current to flow through the indicator lamp, indicating the status of the wiring accessory, but does not allow DC current to flow through the indicator lamp. By blocking DC current through the light the isolator means that the light does not carry any current when a high DC voltage is applied to test the insulation, which may cause incorrect readings.