Cantilever 2801 & 2802

Signal 2801 is two blocks east of East Winslow and the beginning of CTC. If East Winslow is all red, signal 2801 should display a flashing yellow, or advance approach. But to do so might mean that 2801 could flash yellow for hours on end, even if there was no westward train in the vicinity. This would not be good for a US&S FN-27 or FN-28, the device that causes the yellow to flash. Operation of the FN-27 is quite simple: the relay rocks a front and a back contact on and off continuously at a steady rate, not unlike a teeter-totter. The FN-27 is universally reviled by signal maintainers throughout the railroad landscape, for it is prone to failure and constantly needs adjustments. The solution for signal 2801 is to have the flashing unit activated only when a train is on the approach to 2801. So when the system is at rest, 2801 displays a hard yellow, but when a train approaches the signal and the dispatcher has yet to give the train a line-up at East Winslow, the signal changes to flashing yellow