Opinion ID: 1710982
Heading Depth: 2
Heading Rank: 3

Heading: Electronic Tuning Fork

Text: The MARK VI contains a built-in electronic tuning fork system. The heart of the system is a tiny precision tuning fork that is kept in oscillation by an electromagnetic drive coil driven by a transistor oscillator circuit. The tuning fork and drive system are hermetically sealed in a metal case to prevent humidity and barometric changes from effecting the fork frequency. A pick-up coil near the fork provides the doppler signal that is used to calibrate the radar circuit. Pressing the calibrate button turns on the electric tuning fork and applies its accurate calibration signal to the radar amplifier circuit. The frequency of the electronic fork is set for 60 M.P.H. If the meter does not read exactly 60 M.P. H., the radar unit must be calibrated as outlined in the operator's manual. The calibration signal from the electronic tuning fork is accurate to ± .2 M.P.H. at 60 M.P.H. Whenever any of the above methods are used to check calibration, a record should be made of the time, date and equipment used.