No ringing –
Terminal 3 disconnected
Phone ringing continuously.-
Terminals 2 and 5 swapped (2 at one socket connected to 5 on another and vice versa)
Very poor speech quality, possibly poor bell. –
Terminal 3 and 2 or 3 and 5 transposed
Ringing but no speech (or very poor speech) and can’t dial out. –
Wire between terminals 2 or 5 broken.