Wiring LED into buildings on the train track

[lionelsoni]

Check out this topic: http://www.trains.com/community/forum/topic.asp?page=1&TOPIC_ID=17073

[Anonymous]

Is there some easy instructions about wiring LEDs into unlighted buildings. I understand that LEDs cannot be directly connected to a power source w/o a resistor - just wandering if any one has a simple method so that it can be included on a set voltage (or one dialed to the correct voltage) terminal on the transformer.