There were a surprising range of mechanisms for operating turntables, I wonder how many of these are left.
Simplest was a hand-push around. If it was well maintained and balanced, and the loco was equally well balanced on it, it was easier than you might think, though mainly confined to wagon turntables.
The GWR liked hand-powered tables with a winding crank, you could turn a tender loco in a couple of minutes by hand with these, a geared crank at one end, lots of winding by the crew (principally the fireman), and slow rotation of the table.
Next step up were vacuum-powered ones, run off the loco vacuum exhauster, coupled to the loco vacuum hose. they normally seemed to have large vacuum cylinders on the table as well. With the end of vacuum-braked locos presumably these are all gone from the main network. Were there ever any compressed air equivalents?
Electric motor turntables, I've never noticed one in Britain, although standard on the continent.
The turntable at Minehead was too small in diameter for the tender locos that eventually ran (infrequently) on the line, so an interesting challenge for those who don't know, how was the turning of such locos done (which it was).