Fixed Dialing Number

Fixed Dialing Number (FDN) is a service mode of a GSM mobile phone's SIM card.^[1] Numbers are added to the FDN list, and when activated, FDN restricts outgoing calls to only those numbers listed, or to numbers with certain prefixes.^[1] A notable exception is that emergency calls to 000, 112, 911, 999 and the like are exempt.^[2] Incoming calls are not blocked by FDN.^[1]

One practical application of FDN is for parents to restrict the phone numbers their children can dial.^[2] The SIM card's PIN2 must be entered beforehand or when applying such settings.^[2]