at a specific frequency. The receiver is designed to only accept the specific pulse and frequency from its dedicated transmitter. This enables the rejection of spurious infrared light and thus enhances their suitability as components within a safety system. Typically, light curtains are connected to a safety relay which will remove motive power from the hazard in the event that an object is detected. Safety relays can be provided with muting functionality which enables the temporary disabling of the safety function to allow objects to pass through the light curtains without tripping the safety relay. This is particularly useful for machinery which has some semi-automatic procedures. Standards The following partial list of standards should be used for guidance when implementing light curtains: ANSI B11.19 IEC61496-1/-2 IEC/TS 62046; ISO13855 (EN 999); References Occupational safety and health Safety equipment de:Lichtvorhang