In 1961, Parks Medical Electronics, founded in 1961 by Loren Parks, is the world’s oldest manufacturer of Doppler Ultrasound Systems. The company, established initially as Parks Electronics Laboratory, manufactured impedance plethysmographs, mercury strain-gage plethysmographs, hearing testers, EKG telephone telemetry and exercise EKG telemetry in the years before Doppler. Parks made the first directional Doppler in 1965.