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PICList Thread
'tel. call detector'
1999\11\18@004124 by Alan Aldaba

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Hi everyone,

       I'm quite new to the list but been lurking for sometime now, so pls. be
gentle... I'm doing a F84 project that involves the telephone, How can i
detect if the called party have answered the call i made ? What control
signals does a typical telco uses to supervise the line ?

All the best,

1999\11\18@104510 by Duilio Foschi

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At 13.39 18/11/99 +0800, you wrote:
>Hi everyone,
>
>        I'm quite new to the list but been lurking for sometime now, so
pls. be
>gentle... I'm doing a F84 project that involves the telephone, How can i
>detect if the called party have answered the call i made ? What control
>signals does a typical telco uses to supervise the line ?
>
>All the best,
>

at least here in Italy you get no signal at all.

You infer that a call was answered when you don't get any ring back signal
any more (and no busy signal altogether).

Duilio Foschi

1999\11\18@112434 by eplus1

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The ring signal goes away and someone says "hello". <GRIN>
How do you detect the (absence of the) ring signal? That's a better
question.

Call Progress Tones in the US
Dial tone: 350+440Hz Continuous

Busy:
Busy tone: 480+620Hz 0.5s ON 0.5s OFF
Reorder: 480+620Hz 0.25s ON 0.25s OFF

Ring and ring back tone:
Most common: 440+480Hz 2.0s ON 4.0s OFF (the initial ring on some telephone
exchanges may range from 0.5s ON to2.0s ON)
Some PBXs: same frequency, but cadence varies from (1.0s to 1.5s ON and 2.0s
OFF to 3.5s OFF)
Mitel PBXs (When calling from outside) same frequency, but 0.5 ON 0.5 OFF
0.5 ON 1.5s off (burr burr burr burr....)
(Internal calls) 1.0s ON 3.0s OFF

This is from:
hyperarchive.lcs.mit.edu/telecom-archives/TELECOM_Digest_Online/0208.
html

and the other links at
http://204.210.50.240/techref/default.asp?url=pots.htm

I'm not sure if Speech recognition of the word "Hello" would be useful but:
http://204.210.50.240/techref/default.asp?url=io/speech.htm

James Newton spam_OUTjamesnewtonTakeThisOuTspamgeocities.com phone:1-619-652-0593
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{Original Message removed}

1999\11\18@185011 by Mark Willis

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What happens when the software's buggy & calls them every 20 seconds for
a day?  (Something to think about, as well - how do I prevent the
machine from going overboard and annoying the recipient of the call?)

I was given a wrong number for a friends' BBS (Bulletin Board System)
once;  My BBS called these poor people, about every 15 minutes, when not
otherwise in use, they finally asked the Telco to ask me to stop
harassing them.  I wasn't even home at the time, was at the now
ex-girlfriends', a couple doors away;  Oops!  This is an "undesireable"
thing, that you don't want to do.  I put the right number in there &
fixed that.

If no busy signal & no fast busy signal, the call probably went through,
to either a human or a fax machine or voicemail or an answering
machine.  (What are you trying to do with your project?)

Mark

Alan Aldaba wrote:
{Quote hidden}

--
I do small package shipping for small businesses, world-wide.

1999\11\19@045540 by Alan Aldaba

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Hi,

Mark Willis wrote:

>
> If no busy signal & no fast busy signal, the call probably went through,
> to either a human or a fax machine or voicemail or an answering
> machine.  (What are you trying to do with your project?)
>

       Well, i need to detect when the called party answered so that my
project can start the timer..., i'm doing somekind of a logger. BTW,
thanx for your concern.

regards,

Alan

1999\11\19@045600 by Alan Aldaba

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Hi,

"PLUS,E" wrote:
>
> The ring signal goes away and someone says "hello". <GRIN>
> How do you detect the (absence of the) ring signal? That's a better
> question.

       OK,so how can i detect the absence of the ringback or busy signal?

1999\11\19@105442 by James M. Newton

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Well, when the signal is not present for more than the max period of time
between normal occurrences, then it is absent.

Scenix has a routine (that might be converted for the PIC) to detect the
strength of a signal at a specific frequency at:
http://www.scenix.com/virtual/download/dft.html

Scott Datallo has a brilliant page on signal analysis that might be of
assistance at:
www.interstice.com/~sdattalo/technical/theory/sqwave.html
Maybe if we encourage him he will complete the dissertation on Tone
Detection and the Laplace Transforms.

James Newton .....jamesnewtonKILLspamspam@spam@geocities.com phone:1-619-652-0593
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{Original Message removed}

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