What to check
Check the door panel microphone hole (found at the lower left corner of the Entryphone logo) is clear.
Corrective Action
Clear the microphone hole taking particular care not to push the debris further into the unit.
Additional notes
With polished brass panels, there can be a build-up of metal polish and it may be prudent to unmount the loudspeaker
assembly to clear the debris more effectively.
Please note - there are two types of door unit amplifier;
3 terminal - marked E, D and C - 92ETXAMP (pre 2015) and 4 terminal - marked +, -, E & D 10ETXAMP (2015 on)
Links
Spare microphones:
https://www.entryphone.co.uk/shop/productdetail/ETXAMP-MIC
https://www.entryphone.co.uk/shop/productdetail/MIC-PTS