Local area network.

This is a diagram of the LAN dated 23 February 1995.

Buildings on the campus are connected by fibre optic cable to the campus hub.

These inter-building cables had to be well protected, they are the black cables in the photograph.
They terminated in a splicing box. Other flexible cables, the red ones, also terminated in the box.

The fibres were spliced such that the laser light passes undiminished.

The red cables went at ceiling level then down to the racks.

The fibres, in pairs, (transmit/receive) plug in to fots (Fibre Optic Tranceivers) where the signal is converted to an electrical signal. On the bottom shelf a fot labelled E, best seen in FULLSIZE, has a pair of fibres connected on the left and an electrical connection on the right.

The fots are connected to routers there are four routers in this photograph two in the rack in the middle and two in the left hand rack. The routers read the packets and find the destination subnet then sends the packet on its way out of one of its ports. The routers are 'hot', they use Emmiter Coupled Logic to go fast and ECL hardware uses lots of electricity. You can put your hand at rear of the router and feel the heat.

There were six routers connected to an FDDI network.
Fiber Distributed Data Interface provides a 100 Mbit/s optical standard for
data transmission in a local area network. The rest of the LAN was 10 Mbit/s.

There were two standards of ethernet cable ones about as thick as your little finger as in this photograph. Connections to it was by a sting that grey box. It was clamped on the cable and a sharp metal spike pierced the insulation and penetrated the copper conductor. This thicker cable was being phased out.

Another view of the cabling in the hub room

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