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The Arnold rapido N-Scale train line featured electrical devices which were used to control track switch position and train movements. By combining the 0760 Color Light Signal (left) with the 0744 Track Contact Activator and the 0745 Relay, automatic train operation could be achieved.
In such an installation, there would be two track contact activators connected to the relay. The relay is like a switch machine, but instead of throwing the track points, the relay’s coils throw electrical contact points. One pair of these points are connected to the red and green bulbs of the signal. The other set of contacts in the relay are thrown in tandem with the points connected to the signal. So, when the signal is indicating red, the other pair of points are in one position; when the color light shows green, the other contact is made.
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In the drawing to the right, the electrical contact points “A” are being used to control power to a short segment of track. This section is defined by using the 0122 or 0123 Gap Section tracks, with the other end of this segment having an another Gap Section.
When the “A” points are in one direction, the track segment is turned on; in the other position, the track is turned off. The second pair of contacts “B” are used to control the light bulbs. Together, they coordinate the color light signal in such a way that when the signal is green, an approaching train continues in operation. When the signal is red, the power is turned off and the train stops until the signal is set to green again.
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The “A” and “B” contacts are used in both the 0725 Universal switch and in the 0745 Relay. Using the 0725 Universal Switch allows the train operator to control trains by throwing the switch to red or green.
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The 0745 Relay can also be operated by using two 0744 Track Contact Activators. Like the push button, these contactor send a momentary burst of power to one of the coils of the relay. The second contactor sends a momentary burst of power to the other coil of the relay. In this way, a train passing the color light signals can turn that signal red and stop a train which is following behind. Once the train is far enough ahead, it passes over the second 0744 contactor, turning the color light signal back to green, which allows the second train to start. Once that train passes the signal, it turns the signal back to red until it, too, is far enough ahead.
Large model railroads might have a dozen such color light installations, allowing for two or three trains to operate on one track circuit, each following the others at a safe distance without human intervention.
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