Symbol 1560 from ISO 7000 - Title/Meaning: Cab lock Function/description: To identify the control that locks the cab in the open position. To indicate the operational status of the cab.
Additional information: 
On road vehicles: 

red telltale indicates unlocked position; 2) loading platform and rear axle may be omitted if not needed.
Own work using: iso.org/obp/graphics/grs/6e79b91d-f37d-4a37-a492-4c4b0fa925ad 200.png
Vectorization:  Mrmw