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 high-energy reader permits the readhead to have a coating which resists
wear. The reader is generally the insertion type that reads upon
withdrawal, which provides for a steadier motion upon insertion. The
high-energy type reader is often the swipe-through type due to the ability
to read the stronger signals quickly. The swipe reader is more appropriate
to turnstyle applications since a high throughput can be maintained
(approximately 12 per minute nominal).
5.2.2.2 Optical Reader. The optical reader senses either a transparency or
reflectance of light as individual identification codes. Photosensitive
cells read the relative transmissivity of the light and translate this into
the identification. The reader type is usually insertion. Although durable
and low in cost, the badge requires some care to avoid dirt and inks which
inhibit accurate reads.
5.2.2.3 Hollerith Reader. The Hollerith reader operates similarly to the
optical reader. The punched holes permit light passage through the card to
the photosensitive array. Although durable, this card requires prohibition
of bend, fold, spindle, and multilate.
5.2.2.4 Electric Circuit Reader. The electric circuit card reader contains
an edge connector into which the card is literally plugged. The reader
determines the current passage through the circuit as the identification
code. The reader technology is spoofed easily by using electronic
instruments if a valid card can be examined and tested. The card is
generally much thicker than a credit card and thus unsuitable to wallet or
pocket storage. The card is also particularly susceptible to stresses
associated with bending or flexing.
5.2.2.5 Metallic Strip Reader. Electric brushes which make contact to
copper sheets incorporated in the card are the essential components of this
reader. The electrical continuity between the copper sheets and brush
points produce the binary code combination. This reader system is
susceptible to corrosion and other faults which inhibit good electrical
contact to the metallic strips. Outdoor applications are vulnerable to
moisture.
5.2.2.6 Wiegand Reader. The Wiegand reader decodes the card information by
producing a slowly changing magnetic field that affects the specially
treated ferromagnetic wires. When the wires pass by the readhead, a series
of sharp pulses are created which represent binary information. Since there
are no moving parts in the reader, it is not affected by moisture, humidity,
or strong magnetic fields. Care should be taken to protect the associated
data wiring from sources of electromagnetic interference or shared cable and
conduit of fluorescent lighting and electromechanical devices, particularly
electric strikes. The swipe through reader style is effective in indoor and
outdoor applications. There is also an insertion reader available for
recessed wall mounting and "key" style credentials. Custom card designs are
inhibited due to the precise alignment of the code strip required to operate
13.02-74
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