Cheap small light fetal doppler for home use Features: Advanced autocorrelation algorithm for high FHR accuracy High sensitivety wide beam integraded sensor for reliable detection throughout pregnancy. Active noise reduction crystal clear fetal heart sounds Low ultrasound output dosage for ultimate safety Advanced power management for long battery life Elegant and compact design for easy home use Specifications: Fetal Heart Rate Range:50-240bpm Accuracy:±1% or 1bpm whichever is great.s great.s great. Ultrasound Frequency:2.5MHz continuous wave Acoustive output:low power-exemption BS EN61157(Clause 6) Output Headset:100mW(32Ωstereo headset) Audio Response:250Hz-1.25KHZ Physical Size:125*48*32mm Weight:80g(including batteries) Battery 2xAAA 1.5V Alkaline or 2x AAA 1.2V NiCad Auto Shut off:1 minute no signal