After reading the post about producing a good demo, I remembered that when I used to do Uni radio, they had a limiter, and level meters on each channel, so as was cueing up a track, I just had to look at the meter, get it fairly close, and let the technology do the rest. Do clubs do this, a) to protect their speaker systems, and b) to give the DJ's a helping hand.....I did a bit of DJing without limiters/level meters, so you just had to judge the right level by ear (could be embarrassing if you got it wrong, specially as the monitoring was crap.

i think most big clubs use then. club i dj'd @ in yorkshire had one fitted, so we couldn't blow the speakers(or so they thought)

You learn something new everyday

Most use limiters simply because of where they are. Even in innercity locations the are noise restrictions in place and you normaly get enviromental health coming down and setting restrictions which have to be kept too. Limiter's stop over zelous dj's annoyin the neighbours.... also stops people blowing the system up too...

I presume that all club use them, and that it's mainly to protect the equipment (and people's ears).

As a DJ (radio or club) you can't just rely on the compressor/limiter; you have to watch the level meters on your mixer.

The compressor may limit the overall peak volume or the music, if you crank up the input too much, it will ruin the dynamics (both the "punch" and the "musicality") of the sound and just sound like a wall of noise (and still be damaging to ears and equipment).

By the time you hear a track in a club it has usually been compressed at least 3 times !! By the time you hear a choon on the radio it has been compressed at least 4 times. It can totally squash the f*ck out of it, even making the overall sound a little different.
When being produced each channel ( every seperate sound ) usually has compression. On the mixdown the whole track is compressed. When the track goes to press and is mastered it is compressed again ( to make sure there are no louder bits in the track ( when making a vinyl master, the audio is played and a master plate has grooves cut into it from these sounds, the louder the sound the deeper the groove / thus badly mastered / compressed vinyls jump ) ) Then when the vinyl reaches the club or radio it goes through a limiter / compressor for safety purposes ( all vinyl / cd's are produced at different levels ). So if its too loud it wont blow the speakers an if its too quiet make up gain raises the level ( makes it louder ) so its not at a completely different level of the track played before it !!

But do DJ's actually use them to get their levels right over 2 records they are mixing?

Not a compressor no. On most mixers you can moniter the amount of signal for both channels on a graphic eq display. Just make sure they are both pretty similar before you bring the other record in....

I've heard the Fridge is the only London club that has a compressor which makes mixing alot easier. Never played there before but would love to to see what it's like.

Yeah the Fridge was lush to play apart from the decks were suspended on the stage and they were moving, only slightly, but had to keep my eyes peeled.

in my opinion one of the best venues in London

would love to play there