www.safetyandhealthmagazine.com/articles/loading-dock-safety-system-3

Loading dock safety system

February 1, 2012
The DSS Trapped Key Loading Dock Safety System is a cost-effective system designed to protect dock workers by using the trapped key concept, meaning the loading dock door cannot be opened until the trailer brakes are locked. Once the trailer brake glad-hand is set, the glad-hand key is released, allowing the loading dock door to be opened. 

Omron Scientific Technologies Inc.