People, please don't jump on Grace about this. Parallel ("T") powering had its day in the film and video industry; it was the only powering method supported by the earliest Nagra recorders and Sennheiser shotguns in the 1960s. But all other professional sound engineers were using phantom powered microphones, which have big advantages especially when multiple microphones are being used. Both Nagra and Sennheiser saw the light and began to support phantom powering in the early 1970s. By the mid- to late-1980s the changeover was essentially complete, and nowadays new T-powered microphones are hardly sold any more if at all.
The fact that a V3 can be configured to support this system, in the rare cases where it may be needed, is a plus. The fact that the preamp can't easily be switched over to parallel powering by people who don't understand microphone powering is an even bigger plus in my opinion because parallel powering can instantly damage or destroy certain types of dynamic microphones. It's not like phantom powering, where both signal leads are charged relative to ground; in parallel powering, the two signal leads are charged relative to each other. The DC is directly superimposed on the audio. It is, in some respects, like putting your fingers into a (low-voltage) light socket.
(You all do know that that's why "phantom" powering is called what it's called, don't you? The idea was that the power would appear when a condenser microphone was plugged in, but a dynamic microphone with a balanced output wouldn't "see" any powering, and could be used safely even if the phantom power switch was left on by mistake.)
--best regards