Telephone and email guide You can search this guide for (part of the) name, phone number, room, department etc. If you are calling from outside The Netherlands first dial +31 24 36 and then the internal phone number. RBS Departments within the Faculty of Science can enter or adjust their guide entries themselves via RBS. All telephone contact persons have a login to edit directory data directly in RBS. The telephone contact person also receives the telephone cost specifications, can request or cancel changes and subscriptions and, if there is reason to do so, receives information from ILS about the telephony facilities within the RU (eg rate changes, malfunctions, maintenance)....