The Sensor Interface Board has sensor interfaces and signal conditioning for light level, sound level, barometric pressure, ultrasonic motion detection and ultrasonic distance measuring built in.

Here is the schematic for this board. Notice that it has a single Polaroid sonar board with 8 reed relays to drive 8 different sonar transducers. This is lust one of the many innovations that we came up with while developing the Gemini robot.