Question: I am interested in purchasing one of your N-Scale single head searchlight signal kits. Could you please tell me what electrical circuitry is required tom run this signal?

Answer from Seth Neumann from Model Railroad Control Systems: You asked Showcase Miniatures about how to drive their N Scale Search light Signals. I work with Showcase on electronics for some of their (beautiful!) signal products. These kits, with some care and attention to detail, build up into very fine and very accurate signals! Their HO and N scale searchlights use this tri-color LED. It's very small -- so it fits into an N scale housing -- the prototype is about the size of a large residential mailbox you would put on a post -- and comes with leads attached, which is the hard part. The chip is "common-anode" which means there is a common + connection and then 3 leads for Green/Yellow/Red, which go off to a signal controller of some sort. Note that you must put a resistor in series with the LEDs*. That said, you want a signal control board that can work with "Common Anode" signals (that is, it will ground the appropriate color lead when the LED is to be lit). Searchlight signals were used for ABS (Automatic Block Signal System) as well as in CTC (Centralized Traffic Control) systems. There are several good ABS controllers including my https://www.modelrailroadcontrolsystems.com/dual-abs-signal-controller-v1-5/ and Modular Signal System (MSS) compliant systems. CTC installations are more varied and generally use some kind of computer control. The more widely used Computer Control Systems are CMRI, LCC and LocoNet, all of which support Common Anode Signals.

* you can use a single resistor use 470 ohms at 5V or 1K ohm at 12V in series with the anode if you're OK with the relative brightness of the colors, or you can tune the brightness of each color by putting the LEDs in series with each color so to make one color brighter you might use 680 ohms (at 12V) and another LED dimmer by using a 1.5K in series with it. The issue isn't the LEDs, it's that 20% of males have some degree of Red/Green color blindness so you need to check for yourself (and your core operators) to see what looks right to you.

I hope this is helpful and please get in touch if you need more information.