Korenix JetNet 3705, Руководство пользователя

Страница: 6 / 25

Korenix JetNet 3705 Series Industrial PoE Switch User’s Manual 1-2
Overview
JetNet 3705 Industrial Power Over Ethernet (PoE) Switches have four ports 10/100 TX ports
with PoE injector plus one 10/100TX up-link port( JetNet 3705 ) or four ports 10/100 TX ports
with PoE injector plus one 100FX up-link port (multi-mode “-m” or single-mode “-s” models,
JetNet 3705f ). It is designed to operate under harsh environmental conditions. The switches
provide Power over Ethernet functions to deliver 15.4Watts power budget to powered device
(PD), which is in compliance with IEEE802.3af standard to deliver both of Ethernet data and DC
48V power through the traditional UTP or STP cable to the PD. The IP30-design aluminum case
further strengthens JetNet 3705 's withstand ability in harsh industrial environments. The event
warning is notified to field engineers by relay output triggering field alert system. JetNet 3705
Series Industrial PoE Switch has passed CE/ FCC/ UL safety certifications to help ensure safe
and reliable data transmission for industrial applications. JetNet 3705 Series will be your best
option for industrial network or security system.
Ethernet Switching Technology
To better understand the operation of an Ethernet switch, we need to first differentiate it from a
hub. An Ethernet hub (or repeater) is a device that is used to simply connect Ethernet nodes.
Any message at one hub port is repeated on all ports. That is, hubs forward data packets they
receive from a single station to all hub ports. As a result, all port devices connected to a single
hub will share the same bandwidth. Then as nodes are added to the network hub, they compete
for this finite amount of bandwidth and this can cause data collisions to occur, making network
determinism impossible to attain, especially on busy networks. Now determinism is a term that is
used to describe the ability to guarantee that a packet is sent or received in a finite and
predictable amount of time. The inherent lack of determinism is the main reason that traditional
Ethernet had problems being accepted for use in critical control applications, as most control
systems have a defined time requirement for packet transmission, typically less than 100ms.