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

 

[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.