All of them are either manual unlock (loosen the nut on the bottom, which holds it all together, and rotate the spool with your thumbs in the feed direction) or bump feed like yours. In case you care, yours is the strongest-looking bump feed I've seen. Generally bump feeds are not very durable, but yours looks like an exception. Being a very amateurish user of trimmers, I prefer to use a bump feed - but I prefer to own a manual feed, because I don't expect bump feeds to last.
In general, the better machines have a clutch so that the reel stops when the engine is idling, and that enables you to feed manually without stopping the engine, if you choose.
