This International Standard, IEC 1266, specifies methods of evaluating the performance of ultrasonic foetal heartbeat detectors and, in particular, specifies a method of determining the sensitivity of the system to the detection of a moving target.
DS/EN 61266:1995 history
1995DS/EN 61266:1995 Ultrasonics - Hand-held probe doppler foetal heartbeat detectors - Performance requirements and methods of measurement and reporting