Telephone Circuitry: Detecting Hangup

[Zach Zaborny]

Hello, for a project I am building a room monitor: you call the line and the
relay picks it up upon getting the 90vac, and stays on. My question; how
would I go about getting it to detect a hangup? Is there a votlage
fluxuation when the party hangs up? A tone? A polarity reverse? It has been
troubling me for a while.

-Zach

 

[Tomi Holger Engdahl]

"Zach Zaborny" <random@nts-technologies.org> writes:

Hello, for a project I am building a room monitor: you call the line and the
relay picks it up upon getting the 90vac, and stays on. My question; how
would I go about getting it to detect a hangup?

You must mean the hanging up on the caller end...

The problem in this is that there is no single universal
signaling to tell that the caller has hung up.
The telephone system has been originally designed for humans
that are intelligent enough to hangl up when call seems to end.
On some telephone systems very clear signaling is available, some
other not...

Is there a votlage fluxuation when the party hangs up?

Usually not...

A tone?

On some systems there are tones coming after some
time after the caller has hanged up...

A polarity reverse?

Some systems use polarity reversal to signal this I think...
This is not widely supported feature.

It has been
troubling me for a while.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/

 

[Clarence]

"Tomi Holger Engdahl" <then@solarflare.cs.hut.fi> wrote in message
news:lajfz54vz3w.fsf@solarflare.cs.hut.fi...

"Zach Zaborny" <random@nts-technologies.org> writes:

Hello, for a project I am building a room monitor: you call the line and
the
relay picks it up upon getting the 90vac, and stays on. My question; how
would I go about getting it to detect a hangup?

You must mean the hanging up on the caller end...

The problem in this is that there is no single universal
signaling to tell that the caller has hung up.
The telephone system has been originally designed for humans
that are intelligent enough to hangl up when call seems to end.
On some telephone systems very clear signaling is available, some
other not...

Is there a voltage fluxuation when the party hangs up?
Usually not...
A tone?
On some systems there are tones coming after some
time after the caller has hanged up...
A polarity reverse?
Some systems use polarity reversal to signal this I think...
This is not widely supported feature.
It has been
troubling me for a while.

The signal your hoping for is intercepted by the Central office switch.
Nothing comes done the destination line until it times out as a dead
connection, (One end only connected) and that is the tone and voice warning
signal. To hear it just pick up a phone and hold it for long enough.

 

[Watson A.Name - \"Watt Su]

"Zach Zaborny" <random@nts-technologies.org> wrote in message
news:10lf41774vm9a86@corp.supernews.com...

Hello, for a project I am building a room monitor: you call the line
and the
relay picks it up upon getting the 90vac, and stays on. My question;
how
would I go about getting it to detect a hangup? Is there a votlage
fluxuation when the party hangs up? A tone? A polarity reverse? It has
been
troubling me for a while.

-Zach

First off, you should be asking this on the appropriate newsgroup,
comp.dcom.telecom.tech. You're not telling us which party is "hanging
up". If you meant the far end, then most modern telephone switches
don't send anything back to you when the calling party disconnects.