This circuit was taken from the May 1990 issue of "Mainline Modeler".
Parts List: 2-(220 mf capacitors)/2-(68 ohm resistors)/1-(LM3909)
The ends of the capacitors connecting to pin 2 of 3909 are positive.
The article claims this circuit produces a "realistic effect" of the oscillating beam. Experimentation with the value of 220 mf capacitor (connected to pin 8 of 3909) and it's series connected resistor (connected to the positive supply voltage +3) will adjust the oscillation to the effect desired.
