R172 SLK, does B+ to the radio stay on all the time?

[Gatley]

Does anyone know if the red B+ lead to the radio control unit stay active all the time? I am told it may switch off after a time, I need a constant none ignition switched B+ in this region for a tracker. Thanks.

Car is 2015 year SLK250 diesel.

 

[Gatley]

From the VIN it seems the head unit us ab Audio 20 BTW.