 System misuse (duration, angulation) and systems operating outside of intended range can produce thermal and non-thermal effects on fetal tissue, including the possibility for over-heating fetal tissue and introducing mechanical stress on the fetus due to cavitation, radiation force, and acoustic streaming.The use of the word "Sonicaid" for Doppler fetal monitors comes from the products of the UK company Sonicaid Ltd. Sonicaid products included the D205/206 portable fetal Dopplers and FM2/3/4 series of fetal monitors.The company was acquired by Oxford Instruments in 1987 to form Oxford Sonicaid.