From CT Wiki
Nikhef specific information
Calling numbers outside Nikhef
Dial 0 followed by the number you wish to call.
Calling the receptionist
Reception Nikhef 93 or 2163 Reception CWI 92 or 4003 Reception SARA 91 or 3000
From own device *21* [phone2] Cancel from own device #21#
Note: Putting through to an external number needs consent of the direction team.
Putting through while busy
Putting through while busy *22* [phone2] Cancel #22#
Putting through while not picking up
Putting through while not picking up *23* [phone22] Cancel #23#