a repeater is, just that, a station that takes a signal and repeats that
signal on another frequency...usually these repeaters have large antennas
that are mounted high up on towers so that they can receive signals over a
very wide area, and so that they can  retransmit those signals over the same
broad area.
If you have a scanner and program in 2 meter amateur frequencies, most of
them will be repeaters which have an input frequency which they listen and
receive on and an output frequency which they transmit the signal out on.
These repeaters systems are commonly used throughout the radio world for
communications over a wider area instead of the relatively localized ability
of simplex for large areas.
What is simplex? it is a method of communication where both persons who talk
back and forth on their radios are transmitting and receiving, not at the
same time, on the same frequency...ultimately, a repeater allows for 2
people to talk back and forth the same as you can on a telephone without
having to stop transmitting to listen to the other station.
However, most repeaters are semi-duplex, this means only one person can talk
at one time and they must stop transmitting to listen to the other station
transmitting.
As i said, the whole point of a repeater is so that one centralized high
powered transmitter, and a very very sensative receiver can be put up with a
high gain very sensative antenna with allot of height, which will serve a
wide area so that Hams may communicate to other hams relatively long
distances  away without having to have the large antenna systems and the
expensive sensative radio equipment....
hope that helps you to understand a bit better.

You of course need to be a licensed ham to talk on an amateur repeater.
73
Colin, V A6BKX
----- Original Message -----
From: "tomi" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, June 14, 2005 3:07 PM
Subject: repeaters


> Hi, I have heard and read about these thingsyou guiseuse called repeaters.
> How do they work and how can you get on one?
>
> regards: Tomi
>