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Key Control
WP_6006_590x332
OverviewMaster KeyingCross KeyingDownloads

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Visual Key Control (VKC)
For Greater Convenience the key symbol is stamped on the plug face or other visible portion of the front of the cylinder. This makes identification fast and convenient. The disadvantage is that stolen or lost keys can be easily matched to the locks they operate. Also, restamping cylinders when they are rekeyed results in damage to the finish.

Concealed Key Control (CKC)
For greater security, specify CKC on the cylinders. The key symbol is stamped in a concealed location, such as the rear of the cylinder or the side of an interchangeable core.

It is not visible to the general occupants of the building but can be accessed by authorized personnel upon removal of the cylinder or core.
2- and 3-Level Master Keying Systems
To Specify a Simple Master Key System (2 Levels of Keying) The master key symbol consists of TWO letters, such as AA. The change key numbers are added to the master key letters. The numbers come FIRST: 1AA, 2AA, 3AA, etc.

When locks are required which are not operated by the master key or other change keys in the system, they are referred to as “single keyed” and given symbols SKD1, SKD2, etc.

When all higher levels of master keys are to be disallowed, suffix (NMK) to the symbol of the key which is to operate. This means “not master keyed.” Cylinder 1AA(NMK) is operated by 1AA only. The AA master is blocked from operation.

2- and 3-Level Master Keying Systems
To Specify a Grand Master Key System (3 Levels of Keying).
The grand master is assigned any ONE letter, such as A. The master keys under this grand are assigned TWO letters, the first of which must be the same as the grand: AA, AB, AC, etc. are all masters under grand A. Masters BA, BB, BC, etc. are all under grand B. Caution: Do not use the letters I or O because of possible confusion with the numerals 1 and 0, respectively. Change key numbers come after the letters.
For master keys beyond AZ, insert a number between the letters to designate which pass through the alphabet they represent. A2A through A2Z represents the second pass of masters under grand A. A3A through A3Z would be the third. Change keys under these masters have the numbers suffixed in the usual way: A2A1, A2A50, etc.

If the cylinder is to be operated by its change key and nothing lower than the single lettered GMK, the change number is added to the GMK symbol. This is illustrated by the example A1 in the schematic shown.

When locks are required which are not operated by ANY master keys or other change keys in the system, they are referred to as “single keyed” and given symbols SKD1, SKD2, etc.

When all higher levels of master keys are to be disallowed, suffix (NMK) to the symbol of the key which is to operate. This means “not master keyed” and can be applied to any level in the system.

Cylinder AA1(NMK) is operated by AA1 only. The AA master and A grand are blocked from operation.
Cylinder AA(NMK) would be operated by the AA master only. Grand A does not operate.

4-Level Master Keying Systems
To Specify a Great Grand Master Key System (4 Levels of Keying)
The great grand master key is assigned the symbol GGM. The rest of the symbols are the same as those in 3-level systems:

The GMKs are assigned single letters, e.g. A, B, C, D, etc. Caution: Never use X for a grand master key due to the confusion which will result with cross keying symbols presented an the next page.

Masters under each GMK are assigned two letters, the first of which is the same as its respective grand master key. Change key numbers come after the letters. Changes under the grand (A1, B1, etc.) and masters beyond AZ are handled exactly as in the 3 level system already described.

Changes directly under a grand are also handled as illustrated in the 3-level system. For changes directly under the GGM with no intermediate level masters, the change number is added directly to GGM as shown by the example GGM1 in the schematic.
 
When locks are required which are not operated by ANY master keys or other change keys in the system, they are referred to as “single keyed” and given symbols SKD1, SKD2, etc.

When all higher levels of master keys are to be disallowed, suffix (NMK) to the symbol of the key which is to operate. This means “not master keyed” and can be applied to any level in the system. Cylinder AA1(NMK) is operated by AA1 only. The AA master, A grand and GGM are all blocked from operation. Cylinder AA(NMK) is operated by the AA master only. Grand A and the GGM do not operate. Cylinder A(NMK) would be operated by the A grand only, without the GGM.
Selective Master Keys
It is often useful in large keying systems to issue a high level master key to maintenance personnel which allows access across all master and grand master key boundaries of a keying system. A selective master key is usually very close to the system’s top master key, both physically and through its realm of access. Nevertheless, it must be blocked from operating in many areas.

To designate that a lock be operated by a selective master key, suffix the symbol in parentheses to the standard symbol. Example: AA1 (ENG). This must be added every time the selective key is to operate and left off whenever the selective key is NOT to operate. For instance, you may lay out a system in which key AA1 is to operate two different offices. Inside one of them is an electrical cabinet which must be accessible to maintenance personnel carrying the ENG key. That lock must be specified as AA1(ENG) while the lock for the other office must be specified as AA1. Change keys directly under the selective key, such as ENG1, are operated by all higher level keys, such as GGM.

Like cross keying, a selective master key is a convenience feature which decreases the security of the cylinders it operates and limits the expansion and flexibility of the overall keying system.

The most common names and symbols for selective master keys
ENG=Engineer’s key
ATT=Attendant’s key
JAN=Janitor’s key
HKP=Housekeeper’s key
GRD=Guard’s key
MAIN=Maintenance key
Cross Keying
Convenience May Reduce Cylinder Security and Hinder System Expansion
Whenever two or more different keys such as AA1 and AA2 are both required to operate the same cylinder, the cylinder’s security is reduced. This is called cross keying. When the cross keying occurs under all the same higher level keys, such as AAI and AA2, it is known as controlled cross keying. When it combines keys under different higher level keys, such as AAI and AB1, it is known as uncontrolled cross keying.

In addition to reducing the security of the cylinder, cross keying usually imposes limits on the flexibility and expansion of the overall keying system. This is especially true of uncontrolled cross keying. For these reasons, it is strongly recommended to allow personnel to carry more than one key. Cross keying should be discouraged whenever possible. However. when cross keying is required, it is specified as follows, and should be summarized at the beginning of each order.

Case #1
Cylinder requires its own change key. The illustration depicts part of a small medical building where two doctors share a common reception area. The receptionist gets the AA3 key. Each doctor carries a key which operates only one office, but is also cross keyed into the entrance from the corridor.

Determine the symbol of the change key (example: AA3). Then prefix the letter X (example: XAA3). Then list all keys which are to operate in an “operated by...” phrase. Example. “XAA3 operated by AA1, AA2, AA and A”. Note that X is a cylinder specification only. The keys for cylinder XAA3 are designated AA3.

Case #2
A cylinder does NOT require its own change key. This illustration depicts a section of a floor in a dormitory. Each student’s bedroom key operates the hall door lock. There is no need to construct a key which operates only the hall door.

In this case, place an X at both the beginning and end of the symbol and a number between them. Example: X1X, X2X, etc. Again, always include the “operated by . . . phrase with a complete listing of key symbols to operate.