The access control system
2-3
Readers and Reading Heads
Each different card or identification technology is associated with a
different reader.
The 4101-2 Controllers can drive the full range of Cotag Reading
Heads and Loop Antennas. The Reading Head consists of
transmitting and receiving antennas which are driven by a reader
module fitted inside the modular controller. When the cardholder
brings the card within range of the Reading Head the interrogation
signals from the Reading Head activate the card’s microchip. The
number stored in the card is then transmitted to the Reading Head.
4101-2 Controllers can also take inputs from any other card reader
or identification system which has a Wiegand or Magnetic Stripe style
of electrical interface. (Consult the chapter on swipe card modules or
call Technical Support if you need help with an interface.)
Controllers
The controller provides the intelligence and memory needed for the
access control decision, and the drive signals for the reader. It can
also receive input from monitored sensors and provide control of
other devices and systems via its relay outputs. This includes
activating a door lock and monitoring the door status.
One or more controllers are connected via a serial data link to the
supervising computer to make up the complete system.
The computer
The controllers in the system are all linked to a supervising
computer (or computers on a network). The computer is used to set
up the system database and download it to each controller. Most
decisions can then be taken by the controller without reference to the
computer. This means that the system can respond faster and will
continue to work even if the computer or its serial connections fail.
This technique is known as “distributed processing”.
The computer can also be used to monitor information about access
transactions, alarms and other messages from the controllers. Also, if
the computer is off-line, the controllers store this information for later
transmission.
4101-2 Controllers can be managed by a PC running the Access
Control Software or by any other computer system which has
software written to handle the Communications Protocol.
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