The idea of a "voltage sensitive relay" (VSR) or "voltage controlled relay" (VCR) as they are sometimes known, is to simplify the installation, no connection is made to the vehicles alternator .
ALT/TP740-01
7 Pin 12 volt towing plug
12N
Metal bodied
Brass screw terminals
ALT/TP750-01
7 Pin 12 volt towing socket
12N
Metal bodied
Brass screw terminals