SPOTLIGHT INSTITUTIONAL Groundbreaking Solutions for Master Keying cally only need progress one position. If we needed 5-16 (or 6-25 for single increment), we would progress two positions. If we needed 17-64 (or 26-125 for single increment), we would progress three posi- tions. If we needed 65-256 (or 126-625 for single increment) we would progress four positions. If we needed 257-1024 (or 626-3125 for single increment) we only need progress five positions. And so forth. Pattern Possibilities In the LRC we have a similar relationship in both the number of individual key posi- tions and the number of master key posi- tions. However, the individual key positions actually will vary in count because each progression pattern will have that number of available bittings but there are multiple progression patterns. The number of patterns will depend on how many positions we progress and how many we hold constant in each progression. We might, for example, choose to use four posi- tions for individual keys. In such a case, we next have to choose the progression patterns. Do we want to hold one position constant, and progress three? Or two positions con- “The LRC, even without considering the added value of the XMC variant option, seems to this author to me a very useful technique to have in the master keying locksmith’s toolbox. It seems more versatile and safer than the pure rotating constant method.” Holding one constant and progressing three gives us four patterns: RRRC, RRCR, RCRR and CRRR, each yielding the 64 (or 125 in single increment). Holding two constant and progressing two gives us six patterns — RRCC, CCRR, RCRC, CRCR, RCCR and CRRC — with each pattern yielding 16 (or 25 in single in- crement) individual keys. Holding three positions constant and s For LRC, if we chose to use a zone of four positions for individual keys, that would leave one position of master keys in a five-pin cylinder or core, two positions in a six-pin, or three positions in a seven-pin that can be reserved for the master key zone. It is that limitation which makes the LRC so reliable. Consider a six-pin cylinder, using an in- dividual key zone of four positions, which it progresses holding one constant and pro- gressing three, and a master key zone of two. The system can be broken up into a top master with up to four masters under that, with up to four masters under each of those, each offering 256 individual keys under each of those 16 masters — and we still have one position in every cylinder in the system that has no master pins in it. All of this is accomplished with no confusion as to what each master key operates. That is not a bad result. Risk Vs. Reward The simple concept of dividing the key into master key zones and individual key zones is what constitutes the LRC and is what makes the resultant master keys reliable and eas- ily predictable. And the only risk that exists is that some- one attempting to expand it further and not having access to the entire system’s bittings or not familiar with LRC might add bittings or masters that cause interchange. To this writer’s way of thinking, that is an excel- lent reason to never use a “pure” RCM, not a reason to overlook such a valuable tool as the LRC. But remember, that is only one man’s personal opinion, and not the official opinion of the LIST Council or any other official group, organization or association. The LRC also offers an additional capa- bility: It can be created as an XMC variant. (This is my own term for a technique co- developed by A J Hoffman Jr. and Jerome Anderson, and used by Lloyd Seliber at both Ingersoll-Rand’s Schlage division and Dorma Lock, and is not a term recognized 14 KEYNOTES SEPTEMBER 2014 WWW.ALOA.ORG
