Fixed Dialing Number
Service mode of a GSM mobile phone's SIM card
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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]
