Here's more on SRT (just to confuse the issue). Many climbers are asking about the RADS (Rope Ascending Descending System) or YO-YO (up and down on a string) method and how it relates to SRT.While RADS utilizes a single rope its not technically SRT. It is popular with climbers who want the mechanical advantage of DbRT but the convenience of a single line.
Central to the RADS (yo-yo) ascending/descending climbing system is a mechanical belay device like the Petzl Grigri although the Trango Cinch (or similar) can also be used. Rope attachment is by way of the belay device and a hand ascender. A two-to-one mechanical advantage is gained by running the tail of the rope through a small pulley attached to the bottom of the hand ascender (see diagram below or follow the link).
Entering the tree on a single rope using any of the typical 'rope walker' SRT systems requires a high level of fitness and this puts some climbers off. Descending on mechanical ascenders (apart from the Unicender) is also a problem.
That's what makes RADS different. It's much easier on the body and you can descend without too much bother.
Tree climbing purists will argue that RADS is too slow, its hardware dependent and somewhat cumbersome. Regardless of these arguments, RADS has a fairly strong following with both working arborists and recreational tree climbers - just search RADS on the climbing forums like Arbtalk and Treebuzz. Recreational climbers can find out more about RADS at New Tribe.
Remember, this blog is not intended to be instructional. If you want to know more about SRT (or RADS) talk to Drew Bristow at DB Tree, Andy Neverman at thoughtplanters or attend one of Matt Glen's Open Masters events where you can discuss the finer details of SRT with the climbers.