MARBZ101
This plug is a fast and easy way to ensure 13A sokcets are wired correctly. It gives an audible signal in addition to the three neons lighting when the wiring is correct.
MARFD650
Supplied in a robust case complete with transmitter and reciever, it is capable of operating with either the 13A plug top lead for sockets or the TL83 lead for light fittings or other point in a circuit without standard 13A power sockets