I believe the Union Pacific and the Colorado & Southern (and probably many other "busy" single track roads) kept their train order semaphores at the "stop" aspect any time the trainorder office was "open" and manned by an operator. This provided a safety feature that helped prevent a train from going by an open trainorder office and failing to pick up an order. It took at least TWO people to be asleep to miss one that way...the hogger and the operator!
Approaching trains from either direction had to "call for the board" (four short whistle blasts). The response from the operator was either to "clear" the semaphore aspect if no orders were to be delivered or to leave the semaphore displaying the "stop" aspect and
"shine" on the platform with a yellow flag (by day) or a lamp (night)and order delivery hoops or forks in hand (or attached in a delivery stanchion if one was in use), and signal the train ahead against the "stop" aspect of the semaphore.
A common, (but questionable rule-wise) practice was for the operator to "dip" the Train order semaphore in the direction of the train movement (place it momentarily in the "clear" position, then return it to the "stop" aspect) when he had orders to deliver...This was intended to be more easily seen by the oncoming engine crew than the op standing
out on the platform with a flag (day) or a lamp (night).
On other roads, in territory where the train order semaphores were not kept at the "stop" aspect at open T.O. offices, there was usually a rule in place that required the semaphore to be kept at the "stop" aspect for a certain amount of time after the train (the markers on the rear car) that picked up orders there had passed the station before it could be placed back in the "clear" aspect position. This was on the order of a ten or fifteen minute period so that a following movement could not get too close to the other train.
That's right, ain't it Skip???