A good summary of the FAA Advisory Circular 70/7460-1J and ICAO Annex 14,
chapter 6, can be found at this URL:
I had the locals on me a while ago about a tower/light and the info I found
there was all that was required to clear up any misconceptions.
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Administrative requests: towertalk-REQUEST@contesting.com