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Knowledge document #81

Blocking your telephone number from being displayed

You can block your telephone number from being displayed when you make a call. That way, the person you are calling does not see your number in the display of their telephone. This function is called "caller ID blocking" or "CLIR" (Calling Line Identification Restriction). You can either block your telephone number (caller ID) for just a specific call or for all of the calls you make.

Prerequisites

  • The feature "caller ID blocking (CLIR) for individual calls" must have been enabled by your telephony provider.

1 Blocking caller ID for a specific call

You can block your caller ID for just one call. After that call, your caller ID will be displayed every time you make a call:

Configuring a telephone to use the keypad function

Keypad sequences are strings of characters and numbers that you can use to enable or disable functions. You can use keypad sequences immediately with telephones, such as FRITZ!Fon C5, that are registered with the base station of your FRITZ!Box. If you are using a cordless telephone that is not registered with the FRITZ!Box's base station, you must enable the keypad function first:

  1. Configure the telephone so you can send keypad sequences (sequences of characters and numbers, such as *121#) and enter special characters such as * and # with it. On many telephones, you can configure this function in the menu "Operation at a PBX > Dialing options > Dial * and #".

Blocking your caller ID for the next call

  1. When making a telephone call, enter *31# and then the number you want to call. Your caller ID will then be blocked for that call.

    Example:
    Enter *31#0301234 to block your caller ID when calling the telephone number 0301234.

2 Permanently blocking your caller ID (for all calls)

You can also permanently block your caller ID for all calls. To do so, you must enable caller ID blocking, or "CLIR" (Calling Line Identification Restriction), in the FRITZ!Box or your telephone. The procedure depends on the type of telephone you are using:

Note:If you have blocked your caller ID for all calls, you can still display your caller ID for just one call. To do so, simply enter #31# before the number, for example #31#0301234. Your caller ID will now be displayed for this call and blocked again for all other calls.

Enabling caller ID blocking for analog and cordless telephones

  1. Click "Telephony" in the FRITZ!Box user interface.
  2. Click "Telephony Devices" in the "Telephony" menu.
  3. Click the (Edit) button for the respective telephone.
  4. Click on the "Telephony Device Features" tab.
  5. Enable the option "Calling line identification restriction (CLIR)".
  6. Click "OK" to save the settings.

Enabling caller ID blocking for IP telephones

  1. Enable caller ID blocking directly on the IP telephone. Refer to the manufacturer of the device for information on how to set it up, for example consult the manual.

    Note:You can enable caller ID blocking (CLIR) in FRITZ!App Fon by tapping "More > Settings > Tel. No. Suppressed".

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