The switch tower
A single story watchmans shanty was erected at the Junction to control routing and probably signals. In 1909-10 derails were installed and the watchmans shanty raised by 12' according to this memo.
In 1917 these plans were drawn for a two story watchmans tower at this site.
To me this drawing and later pictures like the one below look like the original shanty, rotated 90 degrees, and elevated 12 feet. Maybe the plan was drawn just to get a record of the structure.
The watchmans tower controlled the junctions switches as well as the derails and signals, it was removed when the Junction was interlocked in 1939.
Reproduced with permission of Pennsylvania Trolley Museum