Communications device with adaptive clock frequency

The invention provides a communications device which uses a clock circuit for generating a clock signal, the clock circuit comprising a tuneable oscillator. The clock frequency is varied to make sure it remains within a tolerance range, so that the device can continue to receive messages correctly. An error rate of received messages is determined, and in response to the error rate exceeding a threshold, a setting of the resistor arrangement and/or the capacitor arrangement is changed to change the clock signal frequency thereby to lower the error rate.