[Asterisk-Users] External relay triggered by Asterisk extension - question

[James Bean]

Has anyone every setup an external open/close relay, off say a serial
interface, and have an extension trigger the relay?

Why I ask is I have a student accomodation where I am installing an
asterisk box to supply phone services to the tenants, there is already
an intercom system in the main hallways that triggers the downstairs
door and gate using a standard relay open/close trip, so I was hoping to
get the linux box with asterisk to trip the same type of relay.

Is there any door phones that are speaker driven only and sip based that
anyone knows about as well?

James