A transmitter has an input for receiving a signal, gain controller for applying a first gain to the received signal, a first path for providing a second, relatively high gain for the received signal, a second path for providing a third, relatively low gain for said received signal, a transmitter for transmitting a signal and a controller to cause a received signal to pass through the gain controller and the first path when a relatively high gain is to be applied to the received signal and to cause a received signal to pass through the gain controller and the second path when a relatively low gain is to be applied to the received signal. When a change is made from using one of the first and second paths to using the other, the power of the signal transmitted by the transmitter varies by less than or equal to a predetermined amount.