Repeater

A repeater is a simple but essential networking device. Its job is to deal with a physical limitation of cables: signals weaken as they travel, and beyond a certain distance they become too weak to be read correctly.

The textbook gives the specific limit: signals on a cable can travel a specified distance, usually about 100 metres. Beyond this limit, the signal loses its strength and becomes weak. If you simply let the signal keep travelling, it will eventually fade out and the data will be lost.

A repeater solves this by regenerating the original signal. It is an analog device — it works directly with the electrical signals on the cable, not with the data packets themselves. When a weakened signal arrives at the repeater, the device picks it up, cleans it, and puts a fresh, full-strength copy of the signal back onto the cable. This allows the signal to travel another 100 metres (or whatever the cable's limit is) before needing another repeater. …