Well could I say (with foot in the mouth) that this masterplug attached to portable tools inserted into a 13amp socket uses the human body ,or animal as the earth wire to trip the 10mA RCBO device in the event of an earth fault.( PRCDKB Non-Latching RCD Safety Plug). Rated at 16A it also has a 13 amp fuse with BS 1363 marked on the pins side . I think myself that it is so sensitiive that there is no need for an earth connection.
PROTECTS AGAINST DAMAGING AND DANGEROUS POWER SPIKES: The RCD adaptor is non-latching, so the power needs to be reset after each use, making it ideal for the protection of home appliances
SAFE FOR HOME USE AS MANUFACTURED TO BS 7071 1992: With the one socket for
connecting devices to the RCD adaptor
BUT could Mr pat really ask for £3 for pressing a test button.
Regards
jcm
