As the supply in my car is prone to spikes, I have fitted to the transceiver as protection. the rig is not permanently installed and may be moved between vehicles being pwered through cigar lighter socket. the spikes on my cars supply are very sporadic, however I have lost two hi-fi units in past six years (enough to make this unit wortwhile insurance) won't know if it works only if it doesn't. May consider fitting a second unit to the vehicle itself to protect every thing else in the car when transceiver not being used.