FRITZ!Fon C4 Service - Knowledge Base

FRITZ!Fon C4 Service

Poor speech quality when making and/or receiving telephone calls

One of the following issues sometimes or always occurs when you conduct calls:

  • You experience disturbances such as echo, dropouts, delays or background noise when making telephone calls.
  • A loud and annoying hiss is heard when conducting calls. 
  • The voice of one or both parties sounds distorted or "choppy".

Important:Some of the settings described here are only displayed if the advanced view is enabled in the user interface.

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

1 Installing the latest software for your telephone

2 Disabling HD telephony on your ISDN line

The following steps are only necessary if you are using the FRITZ!Box on an ISDN line and you cannot understand the other party when they speak (very distorted, extremely noisy, robotic voice, or static and crackling can be heard).

  1. Enter #962*2* on your telephone and press the call key (lift the receiver).
  2. Hang up again after about 3 seconds.

    Note:You can re-enable HD telephony by entering #962*1*.

3 Restarting the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" or "Reset" in the "System" menu.
  3. Click on the "Restart" tab (if available).
  4. Click the "Restart" button.

4 Reducing the in-call volume on the telephone

  • Reduce the in-call volume on the telephone as follows: During a telephone call, press the "down arrow" or "telephone book" icon on the control ring.

5 Registering cordless telephones with the FRITZ!Box

  • Register all cordless telephones with the FRITZ!Box's base station and switch off all other base stations.

6 Restoring FRITZ!Fon to its factory settings and re-registering it

The following steps are only necessary if the issue only occurs with a particular FRITZ!Fon, and you do not experience problems with speech quality when using other telephones:

Restoring the telephone to its factory settings

  1. Press the "Menu" key on the telephone.
  2. Scroll to "Settings" and press "OK".
  3. "Reset" > "OK" > "OK"

Deleting the telephone

  1. Click "DECT" in the FRITZ!Box user interface.
  2. Click "Cordless Telephones" in the "DECT" menu.
  3. Click the button (Delete) to delete the relevant telephone.

Restarting the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" or "Reset" in the "System" menu.
  3. Click on the "Restart" tab (if available).
  4. Click the "Restart" button.

Re-registering the telephone

7 Configuring the FRITZ!Box for Internet telephony

The following steps are only necessary if you are using the FRITZ!Box to conduct calls over the Internet (VoIP):

Setting the speed of the line

The following step is only necessary if the FRITZ!Box is not connected directly to a DSL line:

Note:If you are using your FRITZ!Box as a DSL router (standard), it automatically determines these values.

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Account Information" in the "Internet" menu.
  3. Click on "Change connection settings".
  4. Enter the relevant speeds of your Internet connection in the "Upstream" and "Downstream" fields in the "Connection Settings" section.

    Example:
    Enter 2000 for an upstream of 2 Mbit/s; enter 32000 for a downstream of 32 Mbit/s.

  5. Click "Apply" to save your settings.

Setting up a prioritization rule for Internet telephony

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Filters" in the "Internet" menu.
  3. Click on the "Prioritization" tab.
  4. Check under "Real-time Applications" whether a rule for "Internet telephony" is present.
  5. If there is no rule for Internet telephony, click "New Rule".
  6. Select "All devices" (default) as the network device from the corresponding drop-down list.
  7. Select the entry "Internet telephony" from the drop-down list "Enter the network application:".
  8. Click "OK" to save the settings.

Configuring other applications

Applications such as file sharing software and online games establish many simultaneous Internet connections. Although the "Traffic Shaping" function of the FRITZ!Box ensures that voice data is prioritized and evenly transmitted, for technical reasons it can only compensate for disturbances caused by these applications to a certain extent:

  1. Decrease the number of simultaneous connections that are allowed.
  2. Reduce the maximum throughput available to the application.
    • If you still experience disturbances when conducting calls over the Internet:
      • Configure the application as a background application in the FRITZ!Box.

The FRITZ!Box's echo compensation and traffic shaping functions guarantee high speech quality. However, if you still experience an echo, delays or short dropouts, these are caused by the telephone being used, your Internet service provider or telephony provider, and cannot be influenced by the FRITZ!Box.