GRS Type-B Interlocking panel from Niagara Tower on the Lehigh Valley Railroad.
This controlled two interlockings - Niagara Jct. and Tifft Jct., outside Buffalo.
Panel is restored and operating - using two multitrax microcontrollers.
Operation allows switch and signal controls, route locking, and train movements thru interlockings.
From the best of my reseach and knowledge, it operates just as though it was inside the tower.
Speaking of tower....
As pictured in GRS's "Elements of Railway Signaling" 50th Anniversary book:
The Niagara Jct. side of the panel was direct wire, the Tifft Jct. side used GRS Type-H Code:
GRS Type-H code used +/- steps to transmit controls and long/short steps to receive indications.
The line circuit is two-wire series - controls are transmitted by reversing polarity of the line
circuit, indications are transmitted from the field by breaking the line.
There are several different ways this equipment can be wired, depending upon how many
stations or controls are required. The maximum is 64 stations with 4 controls and 13 indications
each (or 32 stations with 5 controls, 16 stations with 6 controls, etc). The less station capacity
required, the more controls and indications that can be use.