The AEB system is operated by a key, and each locomotive has a unique key.
At the beginning of the descent, the LP receives the key from the station master at Castle Rock. Once the AEB is enabled, the LP gives the key to the guard, who holds on to it till the descent is complete.
At the end of the descent, the guard hands over the key to the LP again and the AEB is disengaged. The key is handed over to the station master at Kulem.