What is the difference between a VPIS and a VDS (SM6, RM6 power ON pilot light)?
VPIS (Voltage Presence Indicator System): According to standard IEC 61958 the purpose of a VPIS is to signal a voltage presence. If a lamp is unlit, it does not necessarily mean that no voltage is present (the lamp could have burnt out, for example).
The VPIS is the standard offer.
VDS (Voltage Detector System): According to standard IEC 61243-5 the purpose of a VDS is to reliably check for the absence of voltage in a device. The detector does not have a built-in indicator. Instead it can access information via a terminal on the front panel. The user must test the detector (indicator, voltmeter, etc.) before use.