Mr. Terry DaviesTo ask the Chancellor of the Exchequer when the new switch SL100 for the interface between Government telecommunications network numbers was installed; when the switch failed; and what action is being taken by the Central Computer and Telecommunications Agency as a result of this failure.
§ Mr. BrookeThe SL100 switch on the Government telecommunications network was brought into operation on Monday 27 July 1987. Major problems have occurred on two occasions since then. The first was due to the severe storm on 16 October 1987. As a result of the interruption to the mains power supply throughout Greater London, and the failure of the emergency standby power supplies, the switch ceased to function for some 4½ hours until the mains power supply had been restored. The Central Computer and Telecommunications Agency subsequently worked closely with the Property Services Agency to determine and implement improvements to the emergency standby power supplies.
The second problem occurred on the morning of Thursday 11 February 1988 and continued for most of that day. This seriously affected the majority of telephone calls passing through London on the Government telecommunications network. The CCTA worked closely with the company maintaining the switch to ensure that full service was restored as rapidly as possible, but some random intermittent difficulties on the GTN have persisted since then. The fault was due to corruption of software within the switch and urgent detailed investigations are continuing to determine the cause of this and to clear up the remaining difficulties.