Smart Buildings Systems for Architects, Owners and Builders

hardware (such as a card reader, door position switch, or door strike) and
other inputs and relays as required. The control panel manages the peripheral
devices and communicates between the host computer and the peripheral
devices. The control panels have the following functions:

n Consolidation of all connections to peripheral devices

n Provision of power, as needed, to peripheral devices

n Management of peripherals when communications to the host computer

are absent or when acting in a distributed manner

Although control panels use a standard network connection and are able to
communicate with the host computer or other control panels over the net-
work, the signal methods of a control panel may be proprietary.
Most peripheral devices connected to a control panel do not have a lot of
information to communicate. The device is either “on” or “off ” or “open”
or “closed.” These devices (door contacts, requests to exit, door lock, auxiliary
outputs and inputs) may communicate with a simple dry contact. For example,
when the system detects a “short” across the contact, which indicates an event
(e.g., the door is open), the system can take the required action.
The connection between the control panel and the card reader is more com-
plex, entailing more information flow. The card reader typically uses the
“Wiegand” wiring standard to communicate this information. The origins of
the Wiegand communication protocol derive from card readers in the 1980s
that used the “Wiegand effect” for sensing data. One of the advantages of
the Wiegand standard is that it can be used for long cable runs.
The control panel communicates its status and recent access transactions to
the host computer. The host computer or access server initially configures the
control panel, may continuously synchronize the card holder database, and
performs monitoring, management and administrative functions.

Peripheral Devices

Basic door-related peripheral devices are described in the following subsections.

Door Contacts

Door contacts or door position switches are nothing more than electromag-
netic connections monitoring whether the door is open or closed.

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