In its latest update on last week's major 3G disruption, M1 said Monday that its contingency plans had shortened the restoration of its network to days.

"In the absence of these contingency plans, the services would have taken about 12 to16 weeks to be fully restored," M1 said in a statement. Adding that it takes a "very serious view" of the service incident, M1 said its contingency plans involved increasing network capacity and signalling links between all the other mobile network switches.

M1's service disruption started when one of its vendors was upgrading transmission equipment at its network headquarters in International Business Park at 3am on Jan 15. This caused a power problem which set off gas suppression and water sprinkler systems. One of the telco's mobile network switches then tripped, causing service to be disrupted.

"Plan A" was then activated involving the re-linking its mobile network to an alternative network switch. While the links were being re-configured, Plan B was concurrently activated, it said.

"This involved complex step-by-step restoration work including the reconfiguration of 416 base stations to the alternative mobile network switch, re-establishing communication links, and traffic rebalancing." Comprehensive testing ensued.

Plan B resulted in a total of 199 sites being connected by 3am last Thursday. Then, Plan A took over and completed the remaining 217 sites, it said.