Originally Posted by
EXDAC
There is no "reverser deployment command" in the actual aircraft. The system is a mechanical linkage between the throttle quadrant and the reverser control valves.
I don't know about the Douglas/MacDac aircraft, but Boeing put the air/ground on the hydraulic isolation valve (HIV), not the directional control valve on the cable engine aircraft.
The 737 uses radio altimeter for the air/ground because it has a tendency to float in ground effect and the squat switch doesn't activate - the others use the squat switch.