A Controller Area Network, CAN, transceiver comprising: two terminals for coupling to a CAN bus; a transmitter arrangement configured to transmit signalling on the bus based on transmit data, the transmitter arrangement configured to drive the bus to a dominant state or recessive state based on the transmit signal; an impedance control device; a signalling detector to determine the length of time the transmit data comprises a logic zero prior to a transition to a logic one state and: based on the length of time being longer than a predetermined threshold, provide for control of an output impedance by the impedance control device in accordance with a first scheme; and based on the length of time being shorter than said predetermined threshold, provide for one of: control of said output impedance in accordance with a second scheme; and no control of the output impedance by the impedance control device.