Circuitron
AR-1 Automatic Reversing Circuit

Walthers Part # 800-5400, p. 289 Walthers 2012 HO Scale Reference
A scale, $46.95, currently in stock at Walthers

 
Changes direction when the Opto-Sensor is covered. Use for test track, window display, mine train or automatic reverse loop operation. Pushbuttons can be connected for manual reversing. Requires 12V DC power source. Constructed on 2 x 3" printed circuit board.