A control unit supplies power and data through a rotary transformer to a sensor assembly disposed on a wheel. The data sent by the control unit to the sensor assembly is produced by modulation of the power signal using frequency shift key or amplitude shift key modulation. The sensor assembly converts the received power signal that power to operate the circuitry and sensor assembly, converts the FSK or ASK data signal, and sends sensor data back to the control unit through the rotary transformer by load modulation. The control unit demodulates the load modulated sensor data.