Frequency indicator

The circuit gives a coarse indication of the frequency by a tricolour LED, the Type LF-59EBGBW from Kingbright. When the frequency of the Input signal ts 50 Hz, the two blue LEDs light: when the frequency rises to 500 Hz, the red LED also lights, and when the frequency rises above 5 kHz, the green LED lights, too. The resulting hue is thus indicative of the frequency of the Input signal.