Bridges and Repeaters

LAN's use baseband transmission (pulses) and have typical transmission rates of 100 Mbits/second. WANs using modems and telephone cable transmit at about 10 000 bits/second.

Baseband transmission allows for very fast data transmission but it has one major disadvantage. Electrical pulse flatten out when they travel through a long wire. This, together with other electrical and factors impose a maximum length restriction on LAN's. The maximum length will depend on the type of cable used but it is typically around 1 to 2 km and may be as low as several hundred metres.

Two strategies are used to overcome this length restriction. Repeaters can be installed to clean up and boost the signal at various points. This allows a single network to be extended beyond its normal maximum.

An alternative is to install several smaller networks and link them together using a device called a bridge. A bridge links two similar networks - usually LAN's so that data can flow between the two. Note that unlike a gateway that provides a link between a LAN and a WAN, a bridge will not need to handle different protocols on either side.

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