Fermax City Classic — One-Way Audio Fault (Handset Receive)
System Overview
| System | Fermax City Classic 4+N Door Entry Panel |
| Amplifier Module | REF 9696 (PVT09696) |
| Wiring | 4+N (Building) |
| Power Supply | 12V AC/DC |
Reported Fault
Resident can speak to visitor and be heard clearly, but cannot hear the visitor through their handset. Door buzzer/call tone also reported as quiet.
Root Cause
The REF 9696 amplifier module has two independent trim pots controlling separate audio paths:
| Trim Pot | Controls | Icon on PCB |
|---|---|---|
| Upper | Door panel speaker / microphone volume (visitor side) | Speaker symbol |
| Lower | Handset receive volume (resident side) | Telephone handset symbol |
The lower trim pot controlling handset receive volume had drifted or been incorrectly set, resulting in near-zero incoming audio at the resident handset. The door panel microphone and wiring were confirmed healthy.
Resolution
- Opened front door panel to access REF 9696 amplifier module
- Located lower trim pot (handset speaker volume — telephone handset icon)
- Adjusted clockwise in quarter-turn increments whilst testing from resident handset
- Confirmed two-way audio restored at acceptable volume
Upper trim pot was not adjusted — visitor-side audio was unaffected.
REF 9696 Terminal Wiring Reference
The terminal block runs left to right across the bottom of the module. Labels are printed on the PCB silkscreen:
[ 1 ][ 2 ][ 3 ][ 6 ] [ Cp2 ] [ Ab ][ Ab ] [ ~ ][ ~ ] [ Tc ][ Cp1 ]
| Terminal | Label | Function |
|---|---|---|
| 1 | 1 | 4+N bus — Audio signal |
| 2 | 2 | 4+N bus — Call/tone signalling |
| 3 | 3 | 4+N bus — Door release |
| 4 | 6 | 4+N bus — Common / return |
| 5 | Cp2 | Second door panel connection (second entrance, if fitted) |
| 6–7 | Ab Ab | Auxiliary call button inputs (additional push buttons or second column) |
| 8–9 | ~ ~ | 12V AC/DC power supply input |
| 10 | Tc | Door lock/electric strike relay output |
| 11 | Cp1 | Primary door panel connection (first entrance) |
4+N Bus — How It Works
The four bus wires (1, 2, 3, 6) run from the amplifier module to every handset in the building. Each apartment handset is connected in parallel on these four conductors:
- Wire 1 (Audio): Carries the two-way audio signal between the handset and the door panel microphone/speaker
- Wire 2 (Call/Tone): Carries the call tone signal — activates the handset ringer when the door button is pressed
- Wire 3 (Door Release): Carries the door release signal when the resident presses the door open button on their handset
- Wire 6 (Common): Return/ground reference for the bus
Door Panel Connection
- Cp1 connects to the primary entrance door panel (outdoor call panel)
- Cp2 connects to a second entrance panel, if the building has two entry points
- The door panel contains its own microphone and speaker driven by the amplifier
Power Supply
- The
~~terminals accept 12V AC or 12V DC (marked on the module label) - Label on module: ALIMENTACIÓN / POWER SUPPLY — 12 Vac/Vdc
Door Lock Output
- Tc is the relay output that triggers the electric door strike or magnetic lock
- Activates when any resident presses the door release button on their handset
Notes for Future Visits
- This is a known recurring fault on aged REF 9696 modules — trim pots can wear and fail to hold position after adjustment
- If the fault recurs after trim pot adjustment, replace the REF 9696 amplifier module — it is a direct plug-in replacement
- Also supersedes F-1144 and REF 98589
- Typically £25–40 trade: Door Entry Direct, ADI, or direct from Fermax
- Always confirm both audio directions (resident hears visitor and visitor hears resident) before leaving site
- Check the door buzzer/call tone volume at the same time — it is affected by the upper trim pot and is a useful secondary indicator of module health
Site Reference
Gloucester Court, Gloucester Avenue, Blackpool, FY1 4EH — Flat 12