User's Manual

Planning the Installation

Part No. 430-4G-200-00-000

2.6.2. RS-485

RS-485 has two distinct advantages over the more common RS-232. First, it allows

you to connect up to 31 V-Station 4G devices to a PC with an external RS-232 to RS-

485 converter (available from L-1 EAS). 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:

• Multiple devices must be connected together so that templates can be

distributed among the devices

• The installation has only a single device, but it is over 150 feet (45 meters) from

the host PC.

2-9

2.6. C

HOOSE NETWORK TYPE

If your installation requires the use of network communications, then the choice of cable, the

cable run length, the network topology, and the termination of the network are important

aspects that must be considered. The V-Station 4G and V-Flex 4G devices can be networked

using RS-232, RS-485, or Ethernet protocols.

Table 2-1, below, outlines relevant parameters of the RS-485, RS-232, and 100 baseT Ethernet

communication protocols.

Table 2-1: Communications Network Comparison

Spec RS-485 RS-232 100BaseT

Mode of Operation Differential DC Coupled Single-ended DC Coupled Multi

DC Isolation No No No

Maximum Distance 4000 feet* 150 feet* 4000 feet

Number of Devices on one

line

31 1 Unlimited

Maximum Data Rate

56 Kbps

(recommended)

56 Kbps* (recommended) Auto-negotiated

2.6.1. 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.