Plug-and-play device extends twisted-pair Ethernet

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A standard Ethernet network is limited to a 100m distance for point-to-point transmissions over copper cables; for greater distances, standard UTP Ethernet cables cannot be used, hence an extender is necessary to create a high-speed link between two distant Ethernet networks. However, Westermo is introducing the DDW-120 Ethernet Extender, which uses twisted-pair cables rather than expensive optical fibres or radio links. This plug-and-play unit is suitable for many applications offering data rates from 192Kbit/s to 5.7Mbit/s in both directions over distances of up to 15km. Typical applications include railway signalling, highways, harbours, power stations and extended industrial plants.

Information about the Ethernet link status is forwarded by the Link Fault Forward (LFF) functionality in DDW-120, and is sent over the SHDSL link between two DDW-120 units. In many applications it is a requirement to disconnect the link on the other side of the SHDSL link if the primary Ethernet link goes down. The LFF function uses bits in the SHDSL overhead frame and does not affect the data bandwidth. The opposite unit then reads the bits and the link status will be changed, depending on the received status information. Users can see the LFF status on the LEDs in the front of the unit.

Installation and configuration of the DDW-120 are said to be very simple: no software configuration is required to make the units operational. When long or poor cabling is used, some settings can be adjusted via DIP-switches for optimised performance, while the unit is also supplied with an advanced diagnostic utility that allows installers to analyse the quality of the line and the connection status.

These units are designed for use in harsh industrial environments, and total galvanic isolation and transient protection are standard for all interfaces. The line interfaces are also equipped with extensive protection against over-voltages and transients. The DIN-mounted case makes the unit robust and allows for the surrounding air temperature to be between -40 to 70degC. To allow for uninterrupted communication the units are equipped with redundant power inputs that enable the use of two separate supplies with an operating voltage range of 10 to 60V DC.

Westermo says the DDW-120 is transparent for multicast addressing, VLAN packet and allows VPN pass-through for IPSec. It can also be used with protocols such as Modbus/TCP and Profinet. The units will auto-negotiate the transmission speed but can also be forced to choose a slower (more reliable) or faster (less reliable) data rate. The DDW-120 can be used in point-to-point applications or as a start or termination unit together with the DDW-220/221/222 in daisy-chain applications.

Follow the link for more information about the DDW-120 Ethernet Extender.

03 December 2008

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