Mine is electronic circuit, with a Darlington pair transistor set-up fed by a "master switch controlled" power source which feeds a capacitor. When the master is turned off, the capacitor bleeds off through a resistor set-up, until the voltage drops to a level the circuit shuts off. This is typical timer circuitry, and one minute or so timers are easy and cheap. Getting one that stays on for 10 or so minutes is a lot tougher. It took me some time and help from electronic gurus to develop it. If one went on Ali baba and had someone build 1000 of them, you could probably buy them for $3 each. As it is, I build them by hand and test them with 14 or 28 v. I sell them for $40. It is housed in a plastic box 1 x 2 1/4 x 4 inch box and can be mounted anywhere. I put mine on the copilot foot well wall.