Control collars were devices installed on Leviathan biomechanoids by Peacekeepers. These, often installed alongside paddac beacons, ensured that the Peacekeepers had complete control over the Leviathan and made it impossible for the pilot to operate without Peacekeeper authorization. Control collars also made it impossible for Leviathans to Starburst.
Use of control collars was discontinued during the Peacekeeper Reformation.
Control collars are seen in Farscape.