A remote reversing switch is presented, which is operable at low temperatures and useful for eliminating thermal lead voltages by means of an average. It utilizes four n‐channel enhancement mode MOSFET's with the channels connected in a balanced bridge configuration. Input signal reversal is achieved by gating on alternate pairs of transistors. The use of sapphire heat sinks for all channel leads is critical to the achievement of a switch resolution of better than ±2 nV, measured at 4.2, 77, and 300 K. The switch was also used as a remote chopping element for a phase‐synchronized dc to ac inversion, again at 4.2, 77, and 300 K with resolution approaching the limits of the equipment used to test its performance. The small size, infinitesimal power dissipation, predicted immunity to large magnetic fields, and almost perfect isolation of the driving circuit from the desired signal makes this reversing switch superior to any other device which has previously been used for such purposes.