Hi there

I have just bought a flat that has a very old door entry system that
isn't working properly. The following functions work fine: buzzer
rings when visitor arrives; visitors can hear me speak; i can let
people enter the building; and privacy switch works. However,
visitors can't hear my voice.

I had a look at a neighbours entry phone which works perfectly and i
found it had a small black box (about an inch square) with two wires
in the casing. The box seemed to be added-on (perhaps as a result of
a repair or modification) as is wasn't securly fastened. The two
wires were hooked to the system.

Other than this box, the wiring in my phone is identical to my
neighbour's.

I know this description is really vague, but does anyone have any
suggestions what this little black box does, and more importantly,
what it's called?

thanks

Daljit