The easy-to-operate PM 6307 — Wow and Flutter Meter — is designed to identify and quantify unwanted speed variations in audio and video tape recorders, record players and movie projectors. With its X-tal controlled oscillator giving the choice of 3.00 kHz or 3.15 kHz (DIN standard) it is possible to make very accurate wow and flutter checks and alignments. Readout of speed variations of, for example, a recorder is indicated on two separate analog meters, one for drift and one for wow and flutter. Calibration of the drift indicator is simple, being achieved by depressing the ZERO button, while the SET ZERO control is adjusted for zero indication. The use of the X-tal oscillator eliminates the long warm-up time associated with normal R — C types with the advantage that the instrument can be used immediately after switch-on. The measuring ranges for drift and flutter are separately selectable by pushbuttons. There is also a convenient choice of three positions for wow and flutter measurements. With the filter switched ON, the frequency response is "weighted", according to DIN Standard 45 507. In the filter OFF position, a linear frequency response of 0.5 Hz to > 500 Hz is available and the "unweighted" flutter is indicated. For special measurements beyond the normal everyday usage, there is a connector on the rear panel to apply a desired external filter.