anyone know what this is? security system component?

[sgi_ma]

Hi -
we've moved into a house built in 1990....has a security system, basic smoke deectors as you would expect in the ceilings where you would expect them....and the fixtures pictured below in the walls of each (most) room....not sure what they are....anyone have any ideas?
first picture is the fixture with cover, next few pictures are closeup with cover removed....front and back of the device....thanks!

[HayZee518]

the device is a signalling device for a smoke detector. It has a red led to show when it is tripped and a piezo crystal speaker for the alarm noise.