The Pocket Dop 3 from Nicolet, a handheld digital obstetric doppler, comes standard with a speaker built in that heightens the beating sounds of the fetus's heart to reassure the expectant mother. Its digital display is useful in monitoring heartbeats. It comes standard with probes that can be changed. It has a probe that measures 3 MHz to detect early fetal heart beats. Another probe, the 2 MHz, is intended for use at a later time in the pregnancy or with larger patients. These probes can be angled down behind the pubic bone for the most precise results. Nicolet has been supplying Dopplers for more than 30 years.