[HBQRP] Looking For A Tone Decoder

[Sean Pepin]

On 02/13/2014 07:47 PM, Joe wrote:
> I'm looking for a tone decoder. IE: it hears a certain tone frequency, 
> and it changes state.
>
> Think like a old PL tone thing in a repeater.
>
> Joe wb9sbd

What's your application?

The LM567 is probably capable of what you need. From the datasheet:

The LM567 and LM567C are general purpose tone decoders 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.

Sounds like just what you need, costs about $1.50 in single quantity 
from Mouser.

When I was young I made a cabinet lock that I could whistle to unlatch 
with one of these, but it sort of stinks when the batteries run out.