Subject: From: Date:

Re: [ECS] Panasonic Page Out Dario Greggio Tue, 15 Aug 2000 18:48:29 +0200

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herronf@us.ibm.com wrote:
> 
> I built a Phase Locked Loop circuit using a 567 IC to detect this tone.
> This is connected to Dig In on ECS who picks the relays to connect speakers
> for paging.  The problem I am having is the phase lock loop is drifting off
> the set frequency.  I have changed the 567 once, no help.  Anyone got a
> better idea to detect a tone??  

Well, that circuit usually works well... the only trouble maybe
components varying values (resistor and capacitor). You should try more
accurate parts, with low frequency drift. Or maybe something using a
crystal oscillator: but it's not easy to find a 600Hz crystal, so you
need a different schema and IC.

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Ciao,
Dario
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ADPM Synthesis sas - Torino
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http://www.geocities.com/adpm99

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