What is a self tailing winch ?

Question

And how long have they been around?

Answer 1

Tom is right.  Go to the Harkin website and you can see some photos of them.

Answer 2

When you use a winch on a sail boat to tension up the sheets or other lines, you have to hold the standing part of the line as it comes off the drum. Otherwise, the drum will fill up with line as you tension it up. It takes two people to do it. One to turn the drum and another to "tail" the winch and keep the friction of turns on the drum and pull off the excess turns of line. A self tailing winch does this for you so one person can crank up the tension or slack single handed. They've been around for as long as I've been sailing, some 40 years or more.