Help:Driver AWS Cancel Button
From TrainzOnline
AWS System : Cancel Button
This item is part of the equipment provided to simulate the working of the Advance Warning System (AWS) in British Rail locomotive cabs. See the AWS overview for overall functionality and usage.
This button allows the driver to cancel (acknowledge) an AWS warning. When the AWS system sounds it's horn/buzzer, the driver should press this button within 4 seconds. Failure to do so will apply the emergency brake and stop the train. You can also use the keyboard to cancel (acknowledge) warnings - the default is the Insert key.