An improved slip-ring has a stator and a rotor, and includes a brush having a proximal end mounted on one of the stator and rotor and having a distal end engaging the other of the stator and rotor. The brush is adapted to convey electrical signals across the interface between the stator and rotor. The improvement includes: the rotor including a support member (1); and a track provided on the other of the stator and rotor, the track being arranged for sliding contact with the brush distal end; and a thermal element (3 or 6) arranged within the support member for selectively affecting the temperature of the rotor; whereby the temperature operating range of the slip-ring may be increased.