An energy-sucking torture/restraint device, the variable voltage harness makes sure a prisoner is kept in maximum discomfort.
When the Protectobots captured the "renegade" Blaster and prepared to bring him back to the Ark, Autobot commander Grimlock had a variable voltage harness prepared as punishment for the deserter. Beachcomber, who along with Wheeljack and Cosmos was helping to prepare the device, wondered if it was not a little bit excessive.
When Blaster surrendered to the Dinobots, Grimlock hooked him up to the harness, and essentially threw away the key. Goldbug, after his own surrender to Grimlock, found Blaster still clamped to the device in the Ark's brig. The time spent in isolation had dulled Blaster's sense of purpose.