Vodafone reported that its mobile telephone network reached capacity at about 10 am on the day of the bombings, and it was forced to initiate emergency procedures to prioritise emergency calls (ACCOLC, the 'access overload control'). Other mobile phone networks also reported failures, causing for example BBC Radio London reporters to use landline phones and Sky News to use the station ticker for displaying messages from persons trying to contact their relatives. The BBC speculated that the telephone system was shut down by security services to prevent the possibility of mobile phones being used to trigger bombs. Although this option was considered, it became clear later that the intermittent unavailability of both mobile and landline telephone systems was due only to excessive usage. ACCOLC was activated only in a radius around Aldgate Tube Station because key emergency personnel did not have ACCOLC-enabled mobile phones. The communications failures during the emergency sparked discussions to improve London's emergency communications system.