October152009–InstallationGuideDraft–EditPurposesOnly Page26
Installation Guide – October 2009 – Edit Purposes Only
2009
Spec RS-485 RS-232 100BaseT
Number of
Devices on one
line
31 1 Unlimited
Maximum Data
Rate
56 Kbps
(recommended)
56 Kbps*
(recommended)
Auto-
negotiated
2.1.6.1 RS-232
If your system has only one device, or a few devices (each only a short distance away
from the SecureAdmin PC) then RS-232 can be used, provided that each device can
have a dedicated RS-232 port.
With RS-232 at 9600 baud, a distance of 150 feet is possible with shielded cable, but at
56 Kbps, a maximum of only 20 feet is recommended.
2.1.6.2 RS-485
RS-485 has two distinct advantages over the more common RS-232. First, it allows you
to connect up to 31 4G devices to a PC with an external RS-232 to RS-485 converter
(available from L-1 Identity Solutions). Second, the RS-485 specification allows for
cable
run lengths up to 4000 feet (1200 meters) at modest baud rates.
An RS-485 network is required instead of RS-232 if:
9 Multiple devices must be connected together so that templates can be
distributed among the devices
9 The installation has only a single device, but it is over 150 feet (45
meters) from the host PC.
2.1.6.2.1 RS-485 CABLE SPECIFICATION
V-Station 4G devices provide a 2-wire, half-duplex RS-485 interface. The main cable
run should be low capacitance, twisted-pair cable, with approximately 120 -ohm
characteristic impedance. Category-5 rated communications cable is used in RS-485
networks and its characteristics are defined below. This is the recommended cabling for
RS-485 communications. The cable connection includes a differential line (+ and -) and
a GND connection.
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