A circuit for an ultrasonic channel has a first and a second terminal between which extend a resistive and diode signal paths including a pair of diodes with opposing polarities, for example in anti-parallel. Switching circuitry is coupled with the resistive and diode signal paths and is switchable between first and second states. In the first state, the first and the second terminals are coupled with one another via the resistive signal path. In the second state, the first and the second terminals are coupled with one another via the diode signal path. The switching circuitry includes first and second transistor discharge circuits coupled between first and second drive lines and current paths of these transistors, and coupled to control terminals of these transistors. The control terminals are coupled to the first or second drive line and are non-conductive and conductive in first and second operating states, respectively.