Nec Dterm Series i PABX phone.

Supports 16 incoming lines. Can be powered off 27V DC through socket underneath, centre terminal negative. It uses a 24 character by 3 line LCD display. When powered up but not connected to a PABX nothing lights up, but it has a built in self test mode - hold down the “*” and “#” keys for ten seconds while applying power, then release the keys.

If any referenced page no longer exists, try looking for its URL on http://archive.org.