We have a number of stations, some of them in the same building on a
> single ethernet switch, and some of them in another building somewhere
> else in the world but with internet or intranet connections to that > switch.
> These stations need to be linked with an intercom, using external
> hardware. This should act like a party line, where one unit can press
> a talk button and be heard on all the other units.
> Selective calling features or multiple channels would be nice, but not
> essental. There will be fewer than ten total units in place.
> Does anyone have any suggestion for a device that does this as a
> simple standalone device, preferably with minimum configuration? I
> know Telex makes some VOIP modules which can be integrated with their
> intercom frames, but they all seem to require a central switch.
This should be almost trivially easy to roll your own -- around an IP-enabled micro-controller (something only a little smarter than a Basic STAMP(tm), and using IP multicast.