Inspection or processing device position determining appts.

摘要

The method locates the device which lies behind a wall using two acoustic pick-up devices acoustically coupled to the surface of the wall. A knocker on the inspection or processing device is used to strike the wall. The sound waves emanating from the wall are received by the acoustic pick-up devices. The position of the inspection or processing device is determined by measuring the difference in the transmission time of the acoustic waves to the pick-up devices.