SPOTLIGHT INSTITUTIONAL Groundbreaking Solutions for Master Keying of what we call it, a method, a technique or a variant, it is still the same: It is a way to develop a system that creates a perfectly us- able master key system that holds certain positions constant throughout the system. One of the arguments to this is that some- one not knowing how the system was devel- oped could come along and mistakenly try to expand it using “pure” RCM and rotat- ing the constants throughout, resulting in interchange. But the ALOA technical stan- dards state quite plainly that if you do not have access to all the information of all the keys in the system and how it is developed, you must not expand it: 11. Master Key System Integrity: No at- tempt will be made to expand any master keyed system without first obtaining a valid key bitting array and list of all key bittings currently in use. If this is not possible, the lock shall be keyed SKD or a new master key system generated. Of course, not all of us are ALOA mem- bers and bound by that statement. Nonethe- less, it is simply a good standard business practice not to do something if you are not fully capable of doing it properly. Therefore, this fear should be unjustified. Someone can cause problems in any system if he randomly assigns new bittings without knowing how the system was developed. Now we have the LPP. But it is not the only important variant, just the most common. Brave New World The technique to be discussed next breaks new ground. It is not a technique that has been around since the early days of master keying. However, it takes the advantages of the RCM and uses them, while solving the biggest deficiency of an RCM system. As such, the potential for this technique is outstanding in my opinion. I refer to what I would define (using to- day’s naming conventions) as limited rotat- ing constant, or LRC. The “pure” RCM, due to its difficulty in 12 KEYNOTES SEPTEMBER 2014 “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 easily predictable.” recognizing master key authority limitations, offers a high degree of risk of interchange. For that reason, even though the LIST Coun- cil’s predecessor saw fit to include it in “Ba- sic Master Keying” since 1982, even it only recommends a maximum of a grand master system using it (TMK, one level of incidental master and one level of individual keys). Most soſtware that includes an RCM option only allows one level of master key in it. It cannot be taught or used, it would seem, without issuing dire warnings. Yet it has been taught as a basic master keying technique in courses ever since the Master Keying 101 course developed by the LIST Council’s predecessor in 1982. The LRC, as you will see, has the flexibil- ity and potentially higher level of physical integrity of an RCM system, but makes mas- ter key assignments almost as simple as in TPP. To this writer’s view, that makes the LRC an acceptable skillset and the RCM a questionable one instead. Very few master key systems are simple enough to benefit from a “pure” RCM. The capability of multiple master key levels is needed in virtually every mid- to large-size system. If a system is small enough to be an acceptable candidate for a “pure” RCM, it can instead be developed using LPP and expanded only by adding keys that fall un- der the existing master keys, and without adding any levels of additional master keys. If it is not, then either the TPP or the LRC might be a better option. A Deeper Dive So what exactly is an LRC? I stated that it means limited rotating constant. What meaning does that actually convey? In a fully developed “pure” RCM system, we progress the positions using a group of progression patterns whereby a specific number of positions are progressed for indi- vidual keys, while a specific number of posi- tions are “held constant” using the cuts for those positions from the top master key. In each pattern, a specific number of positions progresses, but which positions it is varies from pattern to pattern. Over the entire group of patterns, every position is eventu- ally used for both progressed and constant. In the limited rotating constant (LRC), we limit the number of positions being pro- gressed for individual key bittings. Certain positions will never be progressed to specifi- cally create individual key bittings. Instead, any progression in those positions is reserved for the assignment of master keys of various levels, and all of those positions reserved for master keys are progressed us- ing only one progression pattern. In other words, we have an individual key zone in which rotating constant progression is employed, and a master key zone wherein standard progression is instead used. That makes it a little less versatile than TPP be- cause by its very name, we know it is a lim- ited system. But at the same time, it allows for safe usage of master keys — which RCM does not — and still has some solid constant positions to increase the physical integrity of the cylinder (see Figure 1). The Difference There is nothing new about the concept of dividing the key into zones. What makes this technique unique is that in the individual key zone, we will progress the bittings using WWW.ALOA.ORG
