ACCOLC (Access Overload Control) is a British procedure for restricting mobile telephone usage in the event of emergencies. It is similar to the GTPS (Government Telephone Preference Scheme) for landlines.

This scheme allows the mobile telephone networks to restrict access in a specific area to registered numbers only and is normally invoked by the Police Incident Commander (although it can be invoked by the Cabinet Office). The emergency services are responsible for registering their key numbers in advance.

How it works

Mobile telephones work on a cell basis. The cells adjacent to the incident are identified and ACCOLC is implemented on those cells alone. ACCOLC enabled telephones are allowed access to the network and all other users will receive service busy or not available tones. Once the call is connected to the network it is routed like any other.

ACCOLC is indicated on the SIM card by a number in the range 0 - 15. Ordinary cellphone users have numbers in the range 0 - 9. Higher priority users are allocated numbers 10 to 15 During an emergency, some or all access classes in the range 0 - 9 are disabled. If the overload condition continues, mobiles with access classes level 10, 11, then 12 and so on may also be disabled by the operator.

As ACCOLC can be a frustration to normal network users, it is normally only initiated after careful consideration. In the UK, the authority of a Police "Silver" is required (major incident control is named in three tiers in the UK, gold, silver and bronze, in accordance with the London Emergency Services Liaison Panel, a group responsible for creating best-agreed procedures for dealing with various emergency situations) after consideration with the co-ordinating group.

Not all calling by regular mobiles is prevented. When a user attempts an emergency call (digits are dependent upon the country), the mobile will use a different access class in the 10-15 range, and not the access class in the 0 to 9 range. This smart technology in the phone will ensure that priority is given to mobiles who are attempting an emergency call.


The purpose of the ACCOLC is to restrict civilian access to cell phone networks during emergencies. This actively prevents civilian usage from congesting the cell networks, thus allowing emergency services personnel priority for communications.

See also

External links

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