BLOCKsignalling is a professional manufacturer of model railway electronics accessories based in
the UK.
Our modules are designed to provide the most realistic operation with ruggedness and long-term
reliability key ingredients to ensure that they perform as expected for a long time to come.
Autoreversers are used on DCC layouts to automatically switch the polarity of track feeds in layout
features such as loops, wyes and to provide feeds for turntables.
Whenever a train crosses a section of track where there is a polarity mismatch and a short would
result, the autoreverser automatically switches the polarity to prevent a short circuit and so avoid
subsequent shutdown of the layout.
A short is detected in less than five microseconds, and the polarity is corrected within 10- 20 milli-
seconds. Detection level is approximately 1.75A. For DCC layouts only. For N and OO gauge
scales. Not for use with Hornby HM7000.
Operation
The autoreverser is used to feed the section of track which requires it polarity to corrected to prevent
a short circuit.
In the diagram below, there is a train on the left with multiple power pick-ups, represented by the
yellow wheels.
There is a central section of isolated track, which is fed via the autoreverser and is currently the
opposite polarity its adjacent sections of track.
As the train moves to the right, it crosses rail breaks and enters the central section of track.
At this point, one of its power pick-ups is touching the blue rail and the other is touching the red rail
causing a short circuit.
The autoreverser detects the short and within a few thousandths of a second and switches the
polarity of the central section removing the short.
Wiring - Loops
The diagram below shows the wiring of the Autoreverser for a loop.
There are four track breaks, and in this example the polarity is the same at either side of the breaks at B, and opposite polarity either side of the breaks at A. The points frog is the same polarity as the inside of the loop.
If a train enters through the loop through the points with them set straight through, it will travel over gap B and then around the loop anticlockwise.
When it reaches gap A, the autoreverser will swap the loop polarity to match the diverging route into the points. The frog polarity will also swap and the train can smoothly pass through the points and back to the main layout.
The module is also suitable for connecting Wyes and Turntables to perform automatic polarity switching.
