FRITZ!Box 7490 Service - Knowledge Base

FRITZ!Box 7490 Service

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:The configuration procedure and notes on functions given in this guide refer to the latest FRITZ!OS for your FRITZ!Box.

Simply proceed as described below. After each measure, check whether the issue persists.

1 Plugging the FRITZ!Box in

  • Connect the FRITZ!Box to an electrical outlet. Verify that the socket is live and that other electrical devices function when plugged into it.

2 Installing the latest FRITZ!OS for the FRITZ!Box

3 Testing a different analog telephone

  1. Disconnect the telephone from the FRITZ!Box.
  2. Connect a different telephone to the same port on the FRITZ!Box.
  3. Check whether this telephone makes a sound.
    • 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 also 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 sockets "FON 1" and "FON 2".

4 Configuring ISDN devices

Properly connecting ISDN telephones and other ISDN devices

  • Always connect ISDN devices to the "FON S0" port of your 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:

  1. Remove the ISDN hub and all ISDN devices including their cables from the FRITZ!Box.
  2. 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,
    • or:
      1. Connect all ISDN devices one by one and test each device to find the one that is causing the issue.
      2. Once you have found it, use a different cable to connect the ISDN device to the FRITZ!Box.

Testing a different ISDN telephone

The following steps are necessary if only one device is connected to the "FON S0" port:

  1. Connect a different ISDN telephone (for example from neighbors, friends) to the "FON S0" port on the FRITZ!Box.
  2. 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.

5 Restarting the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" in the "System" menu.
  3. Click on the "Restart" tab.
  4. Click the "Restart" button.