An electrical connector, such as one for receiving a plug, having at least two prongs for insertion into the connector, and having an electrical cable connected to the prongs of the plug and the connector in the usual way, includes a series circuit having an LED. The LED is located within the connector...http://www.google.com.au/patents/US7086892?utm_source=gb-gplus-sharePatent US7086892 - Live circuit indicator for plugs and receptacles
