A general purpose 500 kHz tone decoder designed to provide a saturated transistor switch to ground when an input signal is present within the passband. The circuit consists of an I and Q detector driven by a voltage controlled oscillator which determines the center frequency of the decoder. External components are used to independently set center frequency, bandwidth and output delay.
The LM567 IC is a tone decoder chip which is designed for recognizing a specified frequency band, and activating the output in response to the detection. This IC can be used for a number of different applications, the most common being for remote controls, and security systems.