Why doesn't oil burn and produce smoke at restaurants? At home when you want to deep-fry something, if you leave the heat on for a minute or two more than you should have, the oil starts to burn and produce smoke.

Why doesn't this happen at restaurants and takeaways (UK)? Is it the specialised equipment they use? Or is there more to it? I doubt they turn off the heat on their deep fryers when not in use, cause if someone walks in and orders something that needs deep-frying, it'll take a long time for the oil to get to frying temperatures again!

Any clarification would be greatly appreciated.
Restaurants have massive fans.  

Commercial deep fryers have temperature control.
Example temperature control unit:



And massive heating elements (notice 4 temperature controls): 

  

Massive heating elements allows for even delivery of heat. When you drop frozen fish it has to kick out some heat but it is careful not to get too hot via temperature control. The temperature gradient alone causes good mixing.  When you heat fresh oil you can see it stirring around.    

If your oil is burning and producing smoke then your deep-fryer is too hot.  Even most home fryers have temperature control. Or you are possibly using the wrong oil.  A cheaper home unit will have a smaller heating unit so it will have more trouble with maintaining a constant temperature but a temperature controller near the heating element should prevent any oil from burning.