By default all calls to external recipients from College telephones are presented as 'Withheld'. This can cause problems when telephoning individuals and organisations who do not accept calls from withheld numbers.

However, you can change the Calling Line Identifier, commonly referred to as Caller ID. The options available for Caller ID are as follows:

  • Actual CLI - Present your full College telephone number, which enables the recipient to identify you by your number or call your back directly if your call is missed.
  • Generic College CLI - Present a generic College telephone number (+44 (0)207 594 5555) that does not identify you personally. If your call is missed and the recipient calls this number back, the recipient will hear a message saying that he or she was called by somebody at Imperial College London.
  • Withheld CLI - Continue to present your external calls as 'Withheld'. This is the default setting, so you will not need to change it.

If you choose to select the Actual CLI or the Generic College CLI, you can still withhold your Caller ID on a call-by-call basis by dialling 141 before dialling 9 for an outside line.

Instructions for changing your Caller ID

To change your Caller ID, follow these steps:

  1. Go to
  2. Click on the Select button next to your preferred option.
  3. Wait while your telephone restarts to apply the new setting. Your chosen option will be highlighted.


  • You can only change the Caller ID of a telephone registered to you.
  • You cannot make changes on shared telephones.
  • Changing your Caller ID only applies to external calls. The change will not affect your number presentation on internal calls, including those to Mobex numbers.


If you experience difficulties when changing your Caller ID, contact ICT Service Desk.