What can I do against noise or humming during landline calls via an analogue telephone line?

There are a number of possible causes for a clearly audible noise or humming sound during calls with a telephone connected to the router, e.g. a defect in the telephone or the router. It is not due to the VoIP telephone connection, as the digital technology we use cannot rustle or hum. You would rather perceive interference, e.g. due to insufficient bandwidth, as distortion.

In order to determine the concrete cause of the noise or hum, please carry out the measures described here one after the other.

After each action, please check whether the noise or hum can still be heard. As soon as this is no longer the case, you no longer need to carry out the following measures.

I. Testing the phone

First test whether your telephone is faulty. Simply use another telephone on your router.

If you are using a cordless telephone (DECT telephone) on your router, please set up the base station of the telephone at a greater distance from the router.

II. Check the router:

1. Step:
Please open the router's user interface in an Internet browser. Please enter the IP address of your router in the address bar of the Internet browser.

2. Step:
Please check on the welcome page which firmware version is installed.

3. Step:
If you have a firmware version that has not been updated for more than one year, please perform a firmware update.

III. Error due to connected devices

Turn the power supply of the device halfway around the socket so that the plug contacts are plugged into the other hole of the socket.

Test to see if interference can get to the router via a USB or LAN port, or can be conducted through it.

If one or more devices are connected to a USB or LAN port on the router, disconnect all cables from the USB and LAN ports on the router to test. If no device is already connected to a USB or LAN port on the router, connect a computer to the router for testing.

Please establish a telephone connection. If there is no more noise or humming, the reason was the power supply of another device or a so-called ground loop. The interference either reaches the router via the USB or LAN cable that has now been disconnected or is diverted from the router via the cable that has now been plugged in.

As a countermeasure, please connect your router and all connected devices together to the same socket. Please test different sockets and/or a different socket strip.

If a connected device causes noise or hum, connect the device to the router with UTP-R45 cables (e.g. with the ISDN/analog cable). UTP-R45 cables, which are available from specialist dealers, do not have a ground conductor and therefore do not transmit interference to the router.