Arduino Two Tone Paging

[darkloyo]

Hello dear friends.

I was wondering if is possible to make a two tone (quick call 2) decoder to activate a relay on an Arduino boar. This is for a fire paging.

[wotnot]

Will lives be at risk if this gizmo fails? If so, then stop now.

Cited from -->>

So the answer is 'yes', caveat & subject to the bold text above =)

edit: oops, missed the word 'decoder' -- still yes, but same thing - don't trust lives on these things.

[trash]

I'm not an ardunio person, but this is a pretty simple thing to do with a PIC chip.
A quick look at the tones I would do it one of a couple of ways. The simplest is if you're not wanting to change the code of the relay. Hard wire program it.
That simply involves clipping the audio into a square wave and counting the change of state or zero crossings etc. Double integrating and timing the pulse positions is another.
For a single tone you trigger on a range of positions. If the transitions are 500uS or pulese 1mS then it's a 1KHz tone.

The code would go something like. ...
If you have a carrier detect, then that can start the program else you'll just have to write anti-trip code into the software.

wait:
while( transistion <> 1mS ) wait else {
measure the duration of the 1mS tone
If it is not long enough then return to wait

If the pulse is long enough then delay(short)
if transistion <> 1.2mS then return to wait
else measure the duration of the 1.2mS tone.

If all is good, turn on the relay. (or toggle it)

For arduino I would not be surprised if there is a library for A2D conversion for measuring audio frequency.
All you'd have to do then is write a nice long case() function.

[wotnot]

Interesting stuff, huh...(I remember the sound from the teevee series 'Emergency')



Better to get something other than the arduino to do the heavy lifting -- CMX823

Multiple approaches;

[Reschs]

Why over think the problem.
Cheap MP3 Recorder/Player Module and a switch.
If you must have a code, cheap standalone electronic lock and use the relay out to turn the MP3 Player on.