Sorry about the lack of info. I'm new to this hitech digital phone stuff. On the main box it just says Samsung DCS. It's from the mid/early 90s if thats any help.
About the internal call thing. We're only in quite a small building and we also don't have voicemail boxes for each extension. If someone tries to ring (internal to internal) and can't get thru, they just leave a skype message instead. The main thing is that the receptionist gets a bit fed up with unanswered internal calls coming back to her phone when the person calling may be sat a few yards from her!

[This message has been edited by jonnywaines (edited June 09, 2005).]