I'm certainly no expert on N&W signals of the 1950s but somewhere in my dusty history lessons I recall that there was a heavy Pennsy influence on the N&W (PRR had controlling interests?) so it is my understanding that much of the N&W was signalled using position light signals very similar to the Pennsy's.
Take a peek here. http://www.railroadsignals.us/signals/nwcpl/index.htm
There are quite a few manufacturers of position light signals. Oregon makes a respectable kit form and both NJ International and maybe Tomar has some.
Logicrail has some neat siglal animation circuits that use either IR or photocell detection.
Hope this helps... Ed
For best results you need a 3-lead bicolor LED, since to get a decent yellow you need different brightnesses on the red and green, ie different resistors. The 3-lead LEDs have two LEDs with one side common so you cna do this. There are also signal drivers that work with the 2-lead bicolor LEDs, these use one polarity for red, the reverse for green, and AC for yellow, but it always ends up more of an orange. This can be controlled somewhat by using a non-symmetrical AC but never gets to be a really nice yellow. The newest way is a small SMD type LED that is actually 3 LEDs in one, a red, a green, and a yellow. There are 4 wires, and these can be controlled just like any 3 color signal that has 3 independent LEDs, nothing special needed. They give the best yellow, but the angle changes slightly when viewed close up since the individual elements are next to one another not on top of one another. Not really different than any bi-color LED in that regard.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
The prototype signal used a relay in the signal head that had three colored lenses Red, Yellow and green on a moving arm (vane) that would move infront of a light bulb. With no power to the relay the red lens would be infront of the bulb. Energizing the relay would swing the yellow lens infront of the bulb. Reversing the polarity on the control wires would swing the green lens infront of the light bulb, which is why you sometimes see the signal flash red when it goes from yellow to green.
There are three color LED's that display red,yellow or green in the searchlight signals we use on our layouts. I'm not familiar with the circuitry involved to operate them as I use G type signals with three seperate LED's. Check out customsignals.com .
I am looking to put signals on my new layout. I am just getting started on the layout and am planning ahead. I am modeling the N&W in the late 1950's. I have seen photos of the "target" signals that were used back then. Are there any such signals available today to place on the layout? How would they work? I mean that the N&W signals rotated revealing a different color as was appropriate for the situation. I can't imagine how this would work in HO scale. Also, I have a few places where I am going to need the overhead signal bridges. How does one mount the signals? Are they sometimes one on top of the other (as needed in certain situations)? I can not imagine these HO signals doing anything but changing colors. Help, please.
Craig North Carolina