Hi
You have a Bell Systems door entry system,with bell 801 handsets.the front
panel is a standard surface unit.
Very easy to maintain parts are cheep and readily available phones use a 5
wire system all conected (usually) at the front door call unit which
contains the speech amp and call buttons,A 12v ac transformer is usually
mounted remotely to power the system.
The handsets should "warble" when called and this should be heard at the
fromt door.
If you need any further info repost or check Bell Systems web site.
HTH
CJ