Quartz-controlled tuning fork

Musical instruments are tuned with the aid of a signal source that generates a signal at a frequency of 440 kHz. An electronic tuning fork is superior to its mechanical counter- part as far as dimensions, weight, and stability with temperature are con- cerned. The stability is obtained by controlling the signal source by a quartz oscillator. The output of the oscillator is frequency-divided and then amplified. The output may be made audible by, for instance, a small loudspeaker. In the accompanying diagram, NI, N2, and the quartz crystal form the oscillator. The precise frequency, measured at the Q terminal of FF2 with a calibrated frequency meter, is set with CI. Divider Type 4059 is eas- (B) quartz-controlled tuning fork 34 ily programmed to a different divisor. A duty factor of 50 per cent is en- sured by FF2. The transducer is shunted by a 100 nanofarad capacitor, because most transducers have a much better high- than low-frequency response, which causes very shrill sounds. 24...