Intercom trigged event?

[Foxtastic]

Hi Guys,

I have an apartment with a intercom system. I would like the intercom to trigger events in Homeseer.
Something like: When someone rings... turn down volume, flash a light etc.
The intercom changes in voltage when someone rings... to the question is: Is there something like a voltage sensor that I can use to integrate with Homeseer? Like 1-wire?

Thanks!

[AshaiRey]

What about a small relais.