Specifications

Terminology
38
Liebert Gateway
Also referred to as a router, the Liebert gateway routes information between the Web server and the
Liebert control modules. It uses an Ethernet network and the TCP/IP and BACnet protocols, also
referred to as BACnet over IP.
Half Router
A function of a Liebert gateway. If no Ethernet connection is available to the customer’s network, a
Liebert gateway can communicate using a modem to a second Liebert gateway and serve the function
of one Liebert gateway connected to the backbone.
Media
The physical substance that carries data. SiteScan Web media are Category 5 Ethernet cables and
various types of Shielded Twisted Pair (STP) and Unshielded Twisted Pair (UTP) cables.
Media Access Types
Protocols used to access media. SiteScan Web media access protocols are Ethernet, RS-485, RS-422
and ARCnet156. Ethernet uses a Carrier Sense Multiple Access Collision Detection (CSMA/CD)
schemes where multiple devices sense signals on the media simultaneously, access the media when
they hear no signals and detect collisions that cause retransmission of information. RS-485 and
RS-422 are point-to-point protocols. Point-to-point protocols transmit information directly from one
device to another. ARCnet156 is a token-passing protocol. Token-passing protocols give each device a
designated period to transmit information after it receives permission (a token) based on its physical
address.
Modbus
A building management standard protocol for interfacing devices from different vendors. It provides
client/server communication between devices connected on different types of buses or networks. It is a
request-reply protocol and offers services specified by function codes. Modbus function codes are ele-
ments of Modbus request/reply PDUs.
For more information, go to:
www.modbus.org
Network Management System
Software system to track and configure equipment on a network. It displays information about
devices on the network that have IP addresses and also sends and receives information to SNMP pro-
tocol devices.
Point
Graphics in the SiteScan Web system. For example, a point is one value displayed from the Liebert
unit, such as temperature. The IGM reference library lists possible points for each Liebert unit. Point
also refers to any value obtained via a contact into the SiteScan system; for example, “Temperature”
from a thermistor is a point.
Protocols
Conventions governing the treatment and the formatting of data in an electronic communications sys-
tem. SiteScan Web protocols are Transmission Control Protocol/Internet Protocol (TCP/IP), Building
Automation and Control networks (BACnet), Attached Resource Control Network (ARCnet), and
Information Gathering Module Network (IGMnet). TCP/IP establishes a connection between two
devices and controls the transmission of information using the IP address of each device. BACnet
broadcasts requests for information to devices based on a network or device number (network ID or
object ID) and the devices respond back. ARCnet transmits a token to devices based on their physical
address. IGM sends requests to Liebert equipment based on a set of codes for unit, status, alarm and
control information.