Force collars are a type of psionic disruption restraint used by the Protoss.
Generally used by law enforcement, these devices helped prevent prisoners from using their psychic powers from attacking and escaping. Contained within is a very refined concentration of Rytorium. Once the prisoner's mental energies reach a certain point, the rytorium within causes a powerful feedback disrupting the source's concentration (XCOM - Enemy Within: Neural Feedback). If need be the Force collar can render the prisoner in a stasis field for easier transport (Star Wars: Stun cuffs; Pokémon - Diamond & Pearl: J's technology).