Had a very interesting discussion on several mailing lists as of late. Was asking for clarification on the use of telephone booths and clearance rules on the Milroy "Branch" for planning my operations, I made some very interesting discoveries...
The Employee Timetable for the Middle Division for 1954 breaks out the territories under ABS and MBS operation, and spells out clearance cards and train order protocols for same. But the Milroy "Branch" wasn't listed among them. So what authority was required for operations?
Turns out the Milroy "Branch" wasn't a "Branch", but a "Secondary". It's an important distinction, as the Definitions section of the Book
of Rules defines a "secondary" as a section of track not requiring signals, timetables, or train orders! All that is required to run on a secondary is a verbal order. It is known that LEWIS tower controlled the Milroy "Secondary", so that would be the source for the verbal orders.
The Milroy line had been a "branch" and required clearance cards and train orders up until 1941. At that time, the KV had trackage rights over the line for passenger service. When passenger service was involved, control was more rigid. Once passenger service ceased, the line was changed to "secondary" status and loosened up on the protocols for operations.
So, what was needed to operate on the Milroy Secondary was a verbal order from LEWIS tower.
(In earlier days there were numerous towers along the "branch", as well as semaphore signals, to govern traffic.)
Next, the line had no trackside signals, cab signals, train phones, or radio. The track charts show the locations of numerous telephone boxes. I've confirmed that these operated as a single "party line" to the tower. When used, the crew would have to identify themselves and their location, as the tower would have no other way of knowing.
A train would get an order via telephone at the yard and proceed as instructed. Once they reached their destination, they would use a telephone to call the tower and notify them so the tower could dispatch other trains on the cleared track. New orders could be conveyed to the crew.
My basement has a steel column in it with no obvious way to have it meld into the background. I am pondering using it as a pole to hold a telephone box. When a crew needed to call the tower, they would walk to this telephone box (just as a prototype crew had to walk) and call the tower. Since only one telephone box would be available, it would mimick the "party line" to the tower. Crews would identify themselves and their location and converse as needed.