Some prewar stations are different than later prewar and postwar. The element is heated directly instead of utilizing the resistance of the locomotive field in series with the element.
Two lockons (lets call them A & B) are specified, as well as an insulated section of at least three tracks.
Binding post 1 is for the wire from the middle rail outside of the insulated section (lockon A clip 1).
Binding post 2 is for the wire from the the insulated outside rail inside the insulated section (lockon B clip 2).
Binding post 3 is for the wire from the middle rail inside the insulated section (lockon B clip 1).
The control lever on the roof sets the interval. Lockon A clip 2 is not used. Speed must be kept appropriate to the length of the insulated section, or the train can run through it without stopping. The E-unit should also be off.
To summarize, the station breaks the "hot" circuit from Post 1 to Post 3 (via the heating of the bimetallic strip) when the "ground" circuit to Post 2 is closed by the train wheels entering the insulated track block. The non-insulated rail of the block is continuous with the rest of the layout.
N.B. The insulated section is made by swapping the metal center pins with fibre pins at the start and end of the section as well as the usual fibre pins of the insulated outside rail.