Developing the Site Plan
2-21
RS–232 Interface
Use an RS–232 interface if one or more of the following conditions apply to your site:
• The host computer system is 50 ft (15.2 m) or less from the Encompass 4 Reader.
• The host computer system is more than 50 ft (15.2 m) from the Encompass 4
Reader and a pair of RF modems or limited distance modem/line drivers over
copper wire are used for communications between the Encompass 4 Reader and
the host. The distance from the RF modem to the Encompass 4 Reader should not
exceed 50 ft (15.2 m).
• Other common communications devices that can extend the RS–232 distance,
such as fiber optic modems, have been selected.
The standard RS–232 connection maximum distance depends on the baud rate, cable
type, and the RS
–232 device at the other end.
Note: When extending the RS-232 interface, use a three-pair cable such as Belden
2919. Use a twisted pair for the black (RxD) with ground (black of the black/yellow
pair), and a twisted pair for red (TxD) with ground (black of the black/yellow pair).
The third pair of the three-pair cable can be used for a spare in the event either of the
other two pair are damaged or fail. The cable shield should be tied to a single-point
earth ground on the controller end of the cable.
RS–422 Interface
Use an RS–422 interface if one or more of the following conditions apply to your site:
• The host computer is more than 50 ft (15.2 m) from the Encompass 4 Reader.
• The host computer has an external limited-distance modem.
The standard RS–422 connection maximum distance depends on the baud rate, cable
type, and the RS
–422 device at the other end.
Wiegand Interface
The Encompass 4 Reader can interface with equipment requiring the Wiegand
+5V
DC data0-data1-ground interface. The reader uses the Wiegand interface
included with the RS
–232 or RS–422 option.
Note: The Encompass 4 Reader comes from the factory with either RS–232 and Wie-
gand or RS–422 and Wiegand. If you want to use Wiegand, you must first connect the
Encompass 4 Reader using the RS
–232 or RS–422 interface, set all necessary operat-
ing parameters in the reader, then set the Encompass 4 Reader’s configuration to Wie-
gand, and then connect the Encompass 4 Reader to the Wiegand interface.
Note: You must order tags programmed with Wiegand-formatted data when using a
Wiegand-compatible reader.
Note: When extending the Wiegand interface, use a three-pair cable such as Belden
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