A popular feature of many model railways is an automatic back-and-forth train. A trolley car, commuter train or switch engine shuttles from one end of a point to point track to the other. This adds motion and interest for visitors yet requires no attention from the layout operators.

But why settle for just one train using that track? With the addition of one or two track switches and an Azatrax PFRR controller circuit, up to three different trains or trolleys can take turns traveling across the same single track.
 
DC-powered trains are required because the PFRR control circuit changes the train direction by reversing the +/- polarity of the track power.
 
Train detectors are required at each track end point. Use up to four IR (infrared) sensor sets, or use any devices that close an electrical contact, such as Azatrax MRD1-NV infrared train detectors or magnetic reed switches.
 
One IR sensor set consists of one IR LED paired with one IR receiver. For help installing IR sensors, click here.
 
Station stops: Additional detector circuits can be added between the end points to create intermediate station stops. The train will pause at each station stop, then continue in the same direction.

• Delay time at end points and intermediate stops is user selectable from six to 45 seconds.
• Acceleration and braking effect is user adjustable.

For automated control of a switchback railroad, click here.

Basic back-and-forth, single track

As simple as it gets, a single point-to-point shuttle track. One train or street car travels to one end, pauses several seconds, then reverses direction and travels back to the other end.
 
Required components:

• One PFRR-NTO controller with two IR sensor sets (no station stops),
• or one PRFF-NTO controller with three IR sensor sets (one station stop)
• One DC-powered train or trolley

More station stops can be created between the two end detectors by placing an additional train detector (such as an MRD1-NV detector or a reed switch) at each stop location.

'Pickle Fork RR' for 1 or 2 trains

A single ended pickle fork layout point-to-point track. One or two trains or trolleys take turns traveling from their siding out to the far end and back. If a single train uses the layout, it will alternate between the two sidings at the left.
 
Required components:

• One model PFRR-2W or -3W controller with three IR sensor sets
• One electrically operated track turnout
• One or two DC-powered trains

Intermediate station stops can be created between the two end detectors by placing an additional train detector (such as an MRD1-NV detector or a reed switch) at each stop location.

Double 'Pickle Fork RR' for 1, 2 or 3 trains

A double-ended pickle fork point-to-point layout. One, two or three trains or trolleys take turns traveling from one end of the layout to the other. If only one or two trains use the layout, they will alternately use all four sidings.
 
Required components:

• One model PFRR-2Wor -3W controller with four IR sensor sets
• Two electrically operated track turnouts
• One, two or three DC-powered trains

Intermediate station stops can be created between the two end detectors by placing an additional train detector (such as an MRD1-NV detector or a reed switch) at each stop location.

PFRR-3W controller for layouts with 3-wire switch machines with twin coils, such as Atlas, Bachmann or Peco.

Out-and-back reverse loop for one train A double-ended pickle fork point-to-point layout. One,  train or trolley departs from the tail track, makes a trip around the reversing loop, and returns to the tail track. On its next trip it goes around the loop in the opposite direction.   Required components: One model PFRR-2W or -3W controller with three IR sensor sets One electrically operated track turnout One DC-powered train Intermediate station stops can be created by placing an additional train detector (such as an MRD1-NV detector or a reed switch) at each stop location.

PFRR-2W controller for layouts with 2-wire switch machines.   Circuit board dimensions: 2.9 x 3.6 inches (74 x 91 mm)

Continuous loop with station stops As with the back-and-forth layouts, the train or trolley must be DC powered and one train detector is needed at each stop.   Required components: One model PFRR-NTO controller with one or two IR sensor sets One DC-powered train For more than two station stops, place an additional train detector (such as an MRD1-NV detector or a reed switch) at each additional stop location.   The PFRR circuit provides variable acceleration / deceleration rate and remotely adjusted pause time.

Two trains alternating on one loop

Two trains take alternate trips around a loop. An intermediate stop is optional where trains pause for several seconds then resume their journey. The two trains may run in opposite directions or the same direction.
 
Required components:

• One model PFRR-2W or -3W controller with two IR sensor sets
• A third IR sensor set is needed for an intermediate stop
• Two electrically operated track turnouts
• Two DC-powered trains   

PFRR Back-and-Forth Controller

PFRR-2W for track turnouts that have 2-wire control cables

PFRR-3W for track turnouts that have 3-wire control cables

PFRR-NTO No Turnout option -- for layouts without a track switch.

MRD1-NV single train detector

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