Supertex has introduced the MD0105 two terminal, bi-directional voltage protection device, which draws 200µA while protecting receiver circuitry of ultrasound systems from high voltage transmitter pulses.

It is a normally closed switch governed by a switch control that monitors the voltage drop across terminals A and B. 

The switch will open if the voltage difference exceeds +/-2.0V.  In the open state, 200µA of current will flow through the switch to determine if the high voltage is present.  The switch does not close until the cross-terminal voltage drops below 2.0V.
 
The IC replaces the conventional discrete transmit/receive solution and requires no diode bridges, inductors, resistors or power rails.  The IC typically reduces component counts from up to 48 to one.  Because the IC doesn't require a power supply, MD0105 dramatically reduces noise in ultrasound circuits, thereby enhancing dynamic range.

For more information, see http://www.supertex.com