How to wire MTH Rail King operating crossing signals

How to connect MTH Rail King™ O-scale operating crossing signal flashers and gates to the Azatrax control system

The MTH RailKing™ line of O-scale crossing signals are well proportioned for 3-rail O-gauge and 'high rail' S-gauge (American Flyer™) train layouts and are simple to use. The RailKing™ units differ from most operating grade crossing signals in that they have the flashing circuit built into the signal base. To operate the signal, all you have to do is apply power.
The Azatrax model railroad crossing control system can be used to operate MTH Rail King™ grade crossing signals in a more realistic fashion, especially at crossings with mutiple tracks, than is possible with the stock system. The Azatrax system also allows the train detectors to be placed in the track roadbed, leaving more table space for model structures and accessories.
MTH Crossing Signal Flashers, 30-11010, 30-11006, 30-11014
The first schematic diagram shows how to wire a pair of MTH signals (without crossing gates) to the Azatrax crossing system.
See below for Rail King signals with gates.
This wiring diagram shows the MTH signals powered directly by an MRX1 crossing system controller, which is connected to an AC or DC power supply. The MRX1 watches the train detectors along the track, and turns on the crossing signals when it senses an approaching train.

How many detectors do I need, and where should I put them? It depends on how your trains will operate near the crossing and how you want the signals to respond. See the crossing signal system configuration guide to get started.

MTH Operating Crossing Gate Signal, 30-11012
The RailKing™ 30-11012 O-scale crossing signals have operating gates and are designed for O-gauge 3-rail layouts. They also look good with American Flyer™ S-gauge trains.
These signals have the gate operating motor and the flasher circuit built into the base. The entire unit mounts on top of the layout surface and is very easy to install.
Below are two schematic diagrams showing how to wire the crossing gates to the Azatrax crossing signal control system. The Azatrax system provides more realistic operation of the signals, especially at grade crossings with multiple tracks.
The first wiring diagram uses an MRX1 crossing controller connected to an AC or DC accessory power supply. The controller monitors train detectors which can be hidden in the track roadbed. When the controller senses an approaching train, it operates a relay, such as a MRAPR relay, that switches power to the signal to make the gates go up and down.

The second wiring diagram (below) shows how to use an MRXP expander unit to monitor the train detectors and control the RailKing™ crossing gates. The MRXP is less money than the MRX1 controller, but does require a DC power source in this configuration.

Note that in this application, the MRXP requires a DC power supply.

How many detectors do I need, and where should I put them? It depends on how your trains will operate near the crossing and how you want the signals to behave. See the crossing signal system configuration guide for examples.