FRITZ!Fon C5 Service - Knowledge Base

FRITZ!Fon C5 Service

Humming noise when conducting calls on an analog telephone line

When conducting calls over the analog landline network, either the party using the FRITZ!Box to call or both parties hear a deep humming sound. The noise is clearly audible and not the same as the very quiet and barely perceptible noise that can be heard on all analog landlines. You do not hear the humming noise when conducting Internet calls.

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

1 Checking the landline

  1. Disconnect the FRITZ!Box from the landline.
  2. Connect a telephone to the same line.
  3. If this telephone also does not work when connected to the line, contact your telephony provider and have your line checked.

    ATTENTION!You may be charged for checking. Ask your telephony provider about charges in advance!

2 Connecting all telephones and telephony devices to the FRITZ!Box

  • Connect all telephony devices (for example a telephone, fax) to the FRITZ!Box.

    Important:Connecting additional telephony devices or telephone sockets to the telephone jack can cause errors.

3 Turning off other base stations

  • For testing purposes, turn off other base stations in the vicinity of the FRITZ!Box.

If you now no longer hear humming, place the telephone's base station farther away from the FRITZ!Box and turn it back on.

Note:Alternatively, you can register your cordless telephones directly with the FRITZ!Box and therefore do without the additional base station.

4 Testing whether another device is interfering with the FRITZ!Box

Interference from a device connected to the FRITZ!Box or the power mains may be reaching the FRITZ!Box. Therefore, perform the following test:

  1. Remove all devices and cables from the LAN ports and the USB port on the FRITZ!Box. If no devices are connected, connect a computer to a LAN port on the FRITZ!Box.
  2. If the issue no longer occurs, then a device connected to the FRITZ!Box was transmitting interference to the FRITZ!Box or the computer now channels it off. Usually, you can eliminate the cause of the interference through one of these measures:
    1. Use a power strip to connect the FRITZ!Box and all other connected devices to the same electrical outlet.
    2. Test different electrical outlets and power outlet strips.
    3. Use UTP network cables to connect devices to the LAN ports on the FRITZ!Box. Unlike STP network cables, for example the one included with delivery, UTP network cables do not have a ground wire and do not transmit interference to the FRITZ!Box.

      Important:If the problem occurs with a FRITZ!Powerline adapter, use the UTP network cable included with the FRITZ!Powerline adapter.

    4. If a device connected to the USB port is transmitting interference to the FRITZ!Box, do not connect the device to the FRITZ!Box. Instead, connect it to a USB port on your computer.

If the humming is still present, then the issue is not caused by the FRITZ!Box. Instead, it is caused by a different component (such as telephone, cable, power supply).