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Stephen Freeman -Finescale Model Railway  Trackwork and Signals
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3 Position Semaphore Signals

This is an area which has been the subject of much thought to me over many years.

The Problem

Most Servo Controllers can only cope with two positions. Yes there is the possibility of including a temporary pause but that isn’t really what’s needed.

The Solution?

Given that a servo controller can only cope with two positions how can it be done?

It has occurred to me that by using a second channel it can be.

So you need to split the control (red) wires from one channel to another. This means a second switch or alternatively a suitable rotary switch. Of course you only need to set one of the endpoints on the second channel as the other isn’t needed unless you were modelling a four position semaphore signal (did such a thing ever exist? Not to my knowledge).

Anyway, that’s how I am doing it now.

At the moment it is only really for MERG members as you really need to use a SERVO4 or SEMA4 Board to give you the second channel and the ability to set a suitable 3rd endpoint, some commercial boards do not give you the ability to increase the angular swing./Rotation.