For an airside connection from an arriving T1 flight to a departure from T2, follow T1 transfer security on level 2, then board the B1 train to the Concourse and transfer there to the T2-bound train. Both trains are advertised at around five-minute intervals. The airport says you cannot reverse the journey once aboard, so verify the onward flight's terminal. Travellers without the next boarding pass should ask their airline and refer to the T2 transfer desk after security on level 3.