auto sensing remote turn on amps

It is a helpful feature when installing an amp into a Newer GM vehicle (while retaining the OEM deck)  that allows the radio to remain on after turning the key off.  Normally you would catch an ACC wire, these vehicles do not have a wire that remains on after the key is turned off. 

Pac-audio.com makes a Line Out Converter that has this circuitry built into it.  SOEM-T is the model number.

Bazooka has used this technology for years on their amplified bass tube.  JL had it on the first generation of the 500/1, the unique thing about that amp was that when using it, the amp's remote wire became a remote output to turn on the other amplifiers on the system.