Mike. It's written in a million different tech. manuals & government specification pamphlets . Sadly , these are in a million different places . There is , as yet , no single source & we have to rely on the good auspices of two or three VERY knowlegeable individuals who have spent YEARS studying the facts . These are mainly [but not exclusively] Bonnex , Snufkin & Millsbomber . We all owe them a debt of thanks & also BOCN for assembling a world class website & members that can answer the most obscure of queries in their own field of expertise .Mike.