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 egress. On the following page, Figure 29 presents a simple block diagram of
an access control system. The elements noted in the figure are common to
all automated access systems and discussed in detail in the following
paragraphs.
5.2.1 Coded Badge. Commonly, the access approval relates to a number or
other distinctive information encoded within a badge or token. These
systems often utilize a credit card-sized (3 1/4 by 2 inches) coded
identification credential. The card material is plastic, vinyl, or
polyester composition depending upon environmental characteristics at the
facility and if photo identification images are to be incorporated.
5.2.1.1 Badge Technologies by Type. The coded badge technologies indicated
in Section 2, Figure 8 represent those commercially available. These
technologies are characterized by the information storage which identifies
the distinctive card holder. Coded badge technologies are susceptible to
decoding and duplication given appropriate time, technical expertise, and
funding. The relative susceptibility to decoding and duplication is noted
below as a guide which may be of significant value if an activity requires
more secure credentials. Except as noted below, factory manufacture/coding
does not preclude local assembly to add photographs and printing.
a) Magnetic Stripe. This technology is characterized by a stripe
of magnetic material capable of containing encoded information. The stripe
data are encoded in Aiken Code, a two-frequency, coherent phase recording.
The standards for this encoding relate to the relative position of
information on the stripe. The Track 1 standard is a 210 bits per inch
(BPI) or 79 characters maximum. Track 2 encoding is a 75 BPI or 40
characters maximum. The more common encoding is the Track 2 type as used
and standardized by the American Bankers Association. The categories of
magnetic stripe cards are also broken down into the two encoding energies
used with this media. The low energy (300 oersted) is more common than the
high energy (4000 oersted) type. Obviously, the high energy types are less
susceptible to accidental erasure. Encoders are available to permit a using
activity to produce encoded badges on site, thus saving cost by buying blank
or preprinted stock.
b) Magnetic Spot. This badge refers to a plastic laminated card
which incorporates a sheet of ferromagnetic material with spots strongly and
permanently magnetized on the core material. These spots may be polarized,
and they number between 20 and 100 in a media more stable than magnetic
stripe due to the high energy encoding. Caution should be exercised when
placing this card with bank cards or magnetic tape/stripe media due to the
others' susceptibility to erasure. The magnetic spot badge can be decoded
and duplicated without great difficulty. The badge is manufacturer encoded
but may be assembled on site for photograph or custom printing additions.
c) Optical. Credentials which have rows of spots or lines that
change under specific illumination are optically encoded. The general
optically encoded badge contains spots or lines that absorb, transmit, or
reflect infrared or another specific light spectrum. The change constitutes
the unique code which is facility and card specific. This badge type is
13.02-70
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