Patent ID: 8223958

Claim:
A system comprising: first means for connecting and disconnecting a first pair of conductors of a jack from a second pair of conductors of the jack, the first pair of conductors configured to connect to a first line and the second pair of conductors configured to connect to a secondary line; second means for detecting a voltage or a current on the secondary line while the second pair of conductors is disconnected from the first pair of conductors by the first means; and third means for notifying a user in response to the second means detecting the voltage or the current on the secondary line while the second pair of conductors is disconnected from the first pair of conductors by the first means, wherein the second means comprises: a transistor; a first resistive element coupled between the transistor and one conductor of the second pair of conductors while the second pair of conductors is disconnected from the first pair of conductors; and a second resistive element coupled between the transistor and the other conductor of the second pair of conductors while the second pair of conductors is disconnected from the first pair of conductors, wherein in response to the secondary line being active, a voltage appears across the first resistive element and the second resistive element and current flows through the transistor.