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Communication Interfaces
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12.0 COMMUNICATION INTERFACES
The Liebert STS2 monitoring system offers several choices for communications.
The RS-232 terminal port is standard on all units. The port is located inside the front door, to the left
of the touch screen/LED front panel mounting as shown in Figure 28. This port is primarily used as
an alternate user interface to configure, control, and diagnose the system, especially for systems that
do not include the HMI touch screen. Commands for the RS-232 port are shown in Table 9.
Several other communications options are also available. Those options are located a
Communications compartment to the right of the touch screen/LED front panel and are accessible
when the front panel door is open. See Figures 21 and 22 for the location of the communications
options.
Connections to the communication ports are made by wiring to terminal boards located in the
Communications compartment. The communications options listed below reference the control wiring
drawing for each option.
• Liebert IntelliSlot SNMP/Web/Modbus 485 card (optional) — the card provides connectivity to
any TCP/IP-based Ethernet network to allow the device to communicate with network
management systems (NMS) via SNMP/Web(HTTP). Events can be transmitted to the NMS to
provide remote status monitoring, plus fault and alarm detection. The card includes an RJ-45 port
for an Ethernet connection, via Category 5 cable.
The Liebert SNMP/Web/Modbus 485 card can also integrate the system with an existing Building
Management System (BMS) or out-of-band monitoring, using Modbus, a standard multi-drop
protocol. The card has redundant communication paths that make it possible to connect to a BMS
using Modbus while simultaneously communicating to an NMS through SNMP/Web(HTTP).
See Figure 27 for more information on the Liebert SNMP/Web/Modbus 485 card. If you have
questions about the card, refer to the user guide, SL-52615, available at the Liebert Web site,
www.liebert.com
• Input Contact Isolator (ICI) Board (optional) — provides an interface for up to eight user inputs.
External messages and alarms can be routed to the unit, via the ICI.
See Configuring the Input Contact Isolator Settings on page 96 for instructions on
configuring the connections. See Figure 25 for wiring details.
• Programmable Relay Board (PRB) (optional) — up to two PRBs can be installed in the Liebert
STS2 to route Liebert STS2 events to external devices.
See Configuring the Programmable Relay Board Settings on page 97 for default settings
and instructions for reconfiguring the relays. See Figure 24 for wiring details.
• Comms Board (optional) — includes a terminal block to provide a DTE connection to an external
modem. This board also provides a direct connection to a Liebert SiteScan terminal, via an
RS-422. Liebert SiteLink-12 or Liebert SiteLink-4 is required for Liebert SiteScan to
communicate with the Liebert STS2. See Figure 26 for wiring details.
Data link requirements are Full Duplex Asynchronous RS-232 format.
Communications options are also discussed in 6.0 - Options.
12.1 Using the RS-232 Port
The RS-232 port is configured with a baud rate of 9600 with 8 data bits, 1 stop bit, no parity, and no
hardware handshaking.