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Black Box Explains...DIN rails.

A DIN rail is an industry-standard metal rail, usually installed inside an electrical enclosure, which serves as a mount for small electrical devices specially designed for use with DIN rails.... more/see it nowThese devices snap right onto the rails, sometimes requiring a set screw, and are then wired together.

Many different devices are available for mounting on DIN rails: terminal blocks, interface converters, media converter switches, repeaters, surge protectors, PLCs, fuses, or power supplies, just to name a few.

DIN rails are a space-saving way to accommodate components. And because DIN rail devices are so easy to install, replace, maintain, and inspect, this is an exceptionally convenient system that has become very popular in recent years.

A standard DIN rail is 35-mm wide with raised-lip edges, its dimensions outlined by the Deutsche Institut für Normung, a German standardization body. Rails are generally available in aluminum or steel and may be cut for installation. Depending on the requirements of the mounted components, the rail may need to be grounded. collapse

Product Data Sheets (pdf)...Vertical-Mount Managed Fiber Switch

  • Quick Start Guide... 
  • Hardened VdSl Ethernet Extender Quick Start Guide
    Quick Start Guide for the LB304A, LBPS301A, LBPS304A (Version 2)
  • Quick Start Guide... 
  • 10BASE-T/100BASE-TX Hardened Ethernet Extender over vDSL
    (Version 1)
  • Application Note... 
  • LEH Series Ethernet Swtich Application Note
    Network Redundancy with LEH Series Ethernet Switches (Version 1)
  • Manual... 
  • 100 Mbps Economy Crossover Media Converters
    Installation and User Guide (Feb-02)
  • Quick Start Guide... 
  • 10BASE-T/100BASE-TX Hardened Ethernet Extender Switch (8-Port) Quick Start Guide
    Quick Start Guide for the LB308A (Version 1)
  • Manual... 
  • PoE PSE Switch Manual
    Manual for LPH240A-H and LPH240A-P (Version 1)

Black Box Explains...Layer 2, 3, and 4 switches.

...more/see it now
OSI Layer Physical
7-Application Applicaton Software

LAN-Compatible Software
E-Mail, Diagnostics, Word Processing, Database

Network Applications
6-Presentation Data-
Conversion Utilities
Vendor-Specific Network Shells and Gateway™ Workstation Software
5-Session Network Operating System SPX NetBIOS DECnet™ TCP/IP AppleTalk®
4-Transport Novell® NetWare® IPX™ PC LAN LAN Mgr DECnet PC/TCP® VINES™ NFS TOPS® Apple
3-Network Control
2-Data Link Network E A TR P TR E TR E E E P E P
1-Physical E=Ethernet; TR=Token Ring; A=ARCNET®; P=PhoneNET®

With the rapid development of computer networks over the last decade, high-end switching has become one of the most important functions on a network for moving data efficiently and quickly from one place to another.

Here’s how a switch works: As data passes through the switch, it examines addressing information attached to each data packet. From this information, the switch determines the packet’s destination on the network. It then creates a virtual link to the destination and sends the packet there.

The efficiency and speed of a switch depends on its algorithms, its switching fabric, and its processor. Its complexity is determined by the layer at which the switch operates in the OSI (Open Systems Interconnection) Reference Model (see above).

OSI is a layered network design framework that establishes a standard so that devices from different vendors work together. Network addresses are based on this OSI Model and are hierarchical. The more details that are included, the more specific the address becomes and the easier it is to find.

The Layer at which the switch operates is determined by how much addressing detail the switch reads as data passes through.

Switches can also be considered low end or high end. A low-end switch operates in Layer 2 of the OSI Model and can also operate in a combination of Layers 2 and 3. High-end switches operate in Layer 3, Layer 4, or a combination of the two.

Layer 2 Switches (The Data-Link Layer)

Layer 2 switches operate using physical network addresses. Physical addresses, also known as link-layer, hardware, or MAC-layer addresses, identify individual devices. Most hardware devices are permanently assigned this number during the manufacturing process.

Switches operating at Layer 2 are very fast because they’re just sorting physical addresses, but they usually aren’t very smart—that is, they don’t look at the data packet very closely to learn anything more about where it’s headed.

Layer 3 Switches (The Network Layer)

Layer 3 switches use network or IP addresses that identify locations on the network. They read network addresses more closely than Layer 2 switches—they identify network locations as well as the physical device. A location can be a LAN workstation, a location in a computer’s memory, or even a different packet of data traveling through a network.

Switches operating at Layer 3 are smarter than Layer 2 devices and incorporate routing functions to actively calculate the best way to send a packet to its destination. But although they’re smarter, they may not be as fast if their algorithms, fabric, and processor don’t support high speeds.

Layer 4 Switches (The Transport Layer)

Layer 4 of the OSI Model coordinates communications between systems. Layer 4 switches are capable of identifying which application protocols (HTTP, SNTP, FTP, and so forth) are included with each packet, and they use this information to hand off the packet to the appropriate higher-layer software. Layer 4 switches make packet-forwarding decisions based not only on the MAC address and IP address, but also on the application to which a packet belongs.

Because Layer 4 devices enable you to establish priorities for network traffic based on application, you can assign a high priority to packets belonging to vital in-house applications such as Peoplesoft, with different forwarding rules for low-priority packets such as generic HTTP-based Internet traffic.

Layer 4 switches also provide an effective wire-speed security shield for your network because any company- or industry-specific protocols can be confined to only authorized switched ports or users. This security feature is often reinforced with traffic filtering and forwarding features.


  • Manual... 
  • Media Converter Network Interface Device Manual
    Manual for LGC340A (Version 1)
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