Section 4 - 7
Key Control & Record Keeping
Special Symbols
GGM CTR
AB
AA BA
AA1 AA2 AA3 A1 BA1 BA2 BA3 B1 GGM1 SKD1
Change keys directly under higher level master keys take the name of their associated master key and add
n
umbers after the letter(s). SKD’s, if used, are considered part of the system.
CTR is the symbol for a control key. A top control key, capable of operating all the cores in a system, is
shown in the schematic at the same level as the top master key.
Cross keying
Although sometimes required, cross keying, either controlled or uncontrolled, should be discouraged. Cross
keying greatly reduces the keying capacity of a system, severely limits the security of the cross keyed cylinder
and makes the key system less flexible. Whenever possible, alternate solutions to cross keying should be
explored.
If cross keying is required, each set’s operating parameters need to be defined. The expressions can be
written as follows:
XAA1 oby AA1, AA2, AA, A (oby = operated by)
X1X oby AC1 - AC5, AC10, AC, A
In the second example above, the “X” after the cylinder designation indicates that there is no change key
(CK). It should be noted that cross keying requirements need to be defined at the time bittings are being
generated. Cross keyed cylinders are labeled with the “X” symbol.
Additional Details
The letter “X” should not be used to designate a grand master. As stated above, this letter symbol is reserved
for use in cross keying.
The letters I and O should be avoided for use as grand master or master key symbols as they are sometimes
confused for numbers. To avoid confusion with O, Q should also be avoided.
For systems with more than twenty-four master keys under a given grand, the counting numbers are used
between the letters of the pair. For example, A2A, A2B, A2C….A2Z are the symbols for master keys twenty-
five through forty-eight.
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