Fibre-optic hub extends distances up to 2 km

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30 January 2002 Computer/Embedded Technology

Contemporary Controls has expanded its line of the EI series of industrial Ethernet hubs by introducing a fibre-optic version, the EI6-10T. A hub allows for the expansion of a 10Base-T system beyonjd two nodes or to increase network distances beyond the 100 m limit of the 10Base-T specification. To maximise distance, the typical network uses twisted-pair wiring for the end devices and fibre cables for the inter-hub links. Each twisted-pair can be 100 m in length and the total measurement of inter-hub fibre can be as much as 2000 m. The network diameter cannot exceed 2200 m so in a shared Ethernet environment the span of each fibre segment depends upon the number of hubs used.

This unit's advantage is its ability to link 2 km fibre-optic segments with 10Base-T ports, making it ideal for building control and industrail control applications where distance and robustness are prime concerns. The hub's fibre-optic link provides a level of immunity to lightning and increased immunity to electrical noise and other external influences usually encountered in a commercial or factory environment.

Similar to the EI series in operation, the E16-10T/F is classified as a six-port hub. Four ports support the signalling requirements of 10Base-T and the two fibre-optic ports support the 10Base-FL interface while conforming to the requirements for IEEE-802.3 repeater units. These requirements include preamble regeneration, symmetry and amplitude compensation. By having two fibre ports, a daisy-chain topology can be implemented where the fibre ports are reserved for interbuilding communication with local 10Base-T drops within a building or control panel.

It supplies the required digital pre-emphasis to its 10Base-T transmitting ports in order to compensate for the inherent roll-off signal strength on the twisted-pair cable. Shielded RJ-45 connectors are used to accommodate either UTP or STP cabling. The link integrity function is supported confirming that a functioning adapter or hub is on the other end of the segment. Hubs can be cascaded using a crossover cable.

The E16-10T/F has wide-range low-voltage AC or DC power requirements: AC is 8 to 24 V and DC is 10 to 36 V. There are provisions for redundant power connections and it can be panel or DIN-rail mounted.

There are several Led indicators supplied that aid troubleshooting. Each port has a pair of LEDs to indicate link status and port activity. A separate LED indicates collisions on the network.

It is intended for industrial Ethernet applications and complies with the EMC compatibility standards for immunity and emissions in harsh environments.

For further information contact Electronic Products Design, (012) 665 9700.

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Fibre-optic hub extends distances up to 2 km

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