A device has (1) an electronic key that transmits a wireless coded signal and (2) at least one tool that can receive that signal. The coded signal is compared to a coded signal stored in said tool. If the coded signal matches the stored signal, a switch is closed for a predetermined amount of time. An...http://www.google.es/patents/US7298240?utm_source=gb-gplus-sharePatente US7298240 - Electronically enabling devices remotely
