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'[OT:] : Does such a product exist ?'
2004\07\16@135223 by Gus S.Calabrese

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Greetings to the brain bank

As some of you may know, audio paging
systems sometimes use 70 volts and
transformers to allow multiple speakers to
be connected to the same pair of amplifier wires.

I want to be able to address each speaker individually
using audio tones and turn the speaker on and off.
This would allow me to retrofit a clients paging system
so that we could use audio over ethernet to the amplifiers
and then selectively turn on one speaker to page someone.

The module should get its power from the paging system.

1) Does someone make this product already ?
2) If not, what PIC would be best for detecting tones and
operating a switch ?  I imagine 256 addresses would be
more than sufficient.
3) What tone set would be best ?  DTMF perhaps ?
4) Does anyone have code that would be helpful for this ?
5) Any suggestions on siphoning some audio for power ?



Thanks



Gus S Calabrese
303.964.9670 w/vm   303.908.7716 cell no vm
http://www.omegadogs.com
4337 Raleigh St
Denver, CO 80212

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2004\07\16@144151 by Herbert Graf

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On Fri, 2004-07-16 at 13:51, Gus S.Calabrese wrote:

> The module should get its power from the paging system.
>
> 1) Does someone make this product already ?
> 2) If not, what PIC would be best for detecting tones and
> operating a switch ?  I imagine 256 addresses would be
> more than sufficient.
> 3) What tone set would be best ?  DTMF perhaps ?
> 4) Does anyone have code that would be helpful for this ?
> 5) Any suggestions on siphoning some audio for power ?

I don't know about a ready made solution, however what you describe
shouldn't be too difficult to implement. However, I would not use DTMF,
since decoding that many different combinations of DTMF would need quite
a bit of hardware and/or software.

Would about using a 300bps modem chip? They use FSK which would be fine
for your system. There are quite a few chips out there that would work.
TTYL

-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

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2004\07\16@150515 by Dave Schmidt

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Somebody somewhere has done this with DTMF signaling.  At least they
bought a bunch of my DTMF controlled relay boards for this exact thing.

Dave

> As some of you may know, audio paging
> systems sometimes use 70 volts and
> transformers to allow multiple speakers to
> be connected to the same pair of amplifier wires.

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2004\07\16@225310 by Carey Fisher - NCS

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  > -----Original Message-----
  > From: pic microcontroller discussion list
  > [spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU]On Behalf Of Dave Schmidt
  > Sent: Friday, July 16, 2004 3:05 PM
  > To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
  > Subject: Re: [OT:] : Does such a product exist ?
  >
  >
  > Somebody somewhere has done this with DTMF signaling.  At least they
  > bought a bunch of my DTMF controlled relay boards for this exact thing.
  >
  > Dave
  >
  > > As some of you may know, audio paging
  > > systems sometimes use 70 volts and
  > > transformers to allow multiple speakers to
  > > be connected to the same pair of amplifier wires.
  >


I use the M-8870-01 DTMF Decoder chip from Teltone/Clare.  Works great with
a PIC.
Carey

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2004\07\16@233207 by Dave Lag

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You might want to consider the old (ancient) common carrier tone squelch
originally sub audible tones to release the squelch on specific radio receivers
 should be lots of schematics/ideas in google?
D

At 01:51 PM 7/16/04, you wrote:
>Greetings to the brain bank
>
>I want to be able to address each speaker individually
>using audio tones and turn the speaker on and off.
>This would allow me to retrofit a clients paging system
>so that we could use audio over ethernet to the amplifiers
>and then selectively turn on one speaker to page someone.

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