Ratings system used to identify channels related to their capacity and sensitivity. Relates to the channel's Selyn Draw Speed and Secondary Selyn Storage System Capacity. The equivalent rating for Donors is TN.
(Source: Index card file. Operation High Time --- http://www.simegen.com/sgfandom/rimonslibrary/oht.html) An extraordinarily skilled class of channel, whose abilities were still being discovered and kept secret so as not to spook the Gens.
Mairis Farris is one.