A switch controller includes a primary side including signal transmission circuitry to transmit signals representative of desired transitions of a switch. A signal transformer galvanically isolates the primary side from a secondary side but inductively couples signal transmission circuitry to signal reception circuitry. A switch is coupled to switch a low impedance onto a primary side winding of the signal transformer during pauses between transmissions of the signals representative of the desired transition of the switch. The secondary side includes signal reception circuitry, a drive signal generator to generate a drive signal in response to valid signals received by the signal reception circuitry, and a validation circuit that includes a first comparator, a timer, and a second comparator to compare a timed duration with a threshold duration, and to output to the drive signal generator signals indicative of the validity of particular signals received by the signal reception circuitry.