That is incorrect...
The "lower quadrant" style train order semaphores "failed" to the horizontal or "stop" position due to the heavy counterweight opposite the blade pivot.
If the rod or cable/chain broke while the semaphore blade was pulled down to the "clear" position, the blade would assume the horizontal or "stop" position all by itself.
In normal operation, the operator would pull the blades down agains the counterweight action by means of a rope and handle on a bellcrank inside the station and hook it to hold the blade(s) in the c"clear" position.
When it was necessary to position the semaphore to the "stop" position, the operator merely released the rope from what it was hooked on. and let the semaphore counterweight act to position the blade to the horizontal position. .
Some installations actually hooked the end of the control rope/cable on a hook,, other installations hooked the horizontal arm of the bell crank on a hook in the station ovserhead.
(This was the way the lower quad semaphore at Fort Garland, Colorado was when I personally observed the installation in the late 1960's)