This S gauge
automatic block can control 2 trains on the same track. The block
uses a RR Concepts (rr-concepts.com)
'Switching Interface Module' (aka SIM) to operate the current-switching
to do the stopping and starting.
The automatic block keeps the 2 trains "spaced
apart" on the loop. If a faster
train starts to overtake a slower train, the block stops the faster
train and delays it, until the slower train "regains" the spacing
between trains. Rheostats are used as a crude, but simple
and effective method of slowing down the trains as they enter the
block, and "cushioning" their start as they start-up to exit the block.
-- which is linked from the left menu bar -- probably demonstrates this
more clearly than the verbal description.
The below drawing shows the wiring diagram for the
1-track automatic block demonstrated in the AutoControls YouTube Video
#658 " S Ga. Auto. Block Using RR Concepts SIM" . This wiring diagram
is could probably be improved by adding a 2nd rheostat. Use the diagram
for Project 242, 2-track Automatic Switching Block" as a reference for
wiring the 2nd rheostat.
Interface Module' is essentially a DPDT (Double Pole, Double Throw)
latching relay, with added screw-connection terminals, plus voltage
regulation that allows you to use a range of input voltages to power
it; 6 to 20 volts AC, or 6 to 20 volts DC.
The relay can switch any current, AC, DC, or
DCC. This demonstration was done using using two unmodified
vintage American Flyer engines with the original AC motors, an S-Helper
diesel with a DC motor, and a DCC decoder-equipped American Flyer 283
Pacific. This demonstration was done using a DC transformer,
since all these engines can "happily" operate on DC current.
Activation of the relay is done using
RR-Concepts-supplied magnets and reed switches. The magnets can
be "stuck" to the bottom of an American Flyer car, since they will
stick to the car's metal floor. Note that the magnets I used on
the bottom of the American Flyer cars were the RR Concepts magnets they
sell for LargeScale. (They also supply smaller magnets to use
with HO trains.)
RR Concepts (operated by a gentleman named Curtis
Roeckes in Oceanside CA) has been supplying electronic modules for
LargeScale trains since about 1992.