FRITZ!Box 6890 LTE Service - Knowledge Base
Telephone connected to FRITZ!Box is dead and/or PBX indicates a malfunction
A telephone connected to the FRITZ!Box is dead and/or a PBX indicates a malfunction:
- When you pick up the handset of a telephone connected to an analog extension or the "FON S0" port on the FRITZ!Box, it does not make a sound (for example a dial tone or busy signal). The telephone is "dead".
- The display of an ISDN PBX connected to the "FON S0" port indicates that there is a malfunction.
Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.
Simply proceed as described below. After each measure, check whether the problem persists.
1 Plugging the FRITZ!Box in
- Plug the FRITZ!Box into a power outlet where other devices work.
2 Installing the latest FRITZ!OS for the FRITZ!Box
- Install the latest FRITZ!OS on the FRITZ!Box.
3 Testing a different analog telephone
- Disconnect the telephone from the FRITZ!Box.
- Connect a different telephone to the same port on the FRITZ!Box.
- If you hear a sound, then the first telephone is defective or the cable of the telephone is damaged or incorrectly wired. Try using a different cable or contact the manufacturer of the telephone.
- If you do not hear a sound, check whether the plug of your telephone is correctly wired. The two inner pins carry the analog signal of the RJ11 socket "FON" on the back of the FRITZ!Box.
4 Configuring ISDN devices
Properly connecting ISDN telephones and other ISDN devices
- Always connect ISDN devices to the "FON S0" port of the FRITZ!Box.
- Do not use ISDN cables that exceed a length of 10 m.
- Do not connect more than one ISDN device that must be supplied with power from the FRITZ!Box. You can connect a total of eight ISDN devices to the FRITZ!Box.
- Only use ISDN devices that are suitable for use on a point-to-multipoint line.
Note:Point-to-multipoint lines are common in the private sector and in small offices, whereas ISDN point-to-point connections are used in professional environments.
Connecting ISDN telephones and other ISDN devices individually
The following steps are only necessary if two or more devices are connected to the "FON S0" port:
- Remove the ISDN hub and all ISDN devices including their cables from the FRITZ!Box.
- Test each ISDN device individually and attach it directly to the "FON S0" port (without an ISDN hub).
- If all ISDN devices function individually, test a different ISDN hub.
Testing a different ISDN telephone
The following steps are necessary if only one device is connected to the "FON S0" port:
- Connect a different ISDN telephone (for example from neighbors, friends) to the "FON S0" port on the FRITZ!Box.
- Check whether the telephone makes a sound (for example dial tone, busy signal) when you pick up the handset.
- If you hear a sound, then the first telephone is defective or the cable of the telephone is damaged. Try using a different cable or contact the manufacturer of the telephone.
5 Restarting the FRITZ!Box
- Click "System" in the FRITZ!Box user interface.
- Click "Backup" in the "System" menu.
- Click on the "Restart" tab.
- Click the "Restart" button.