Originally posted by jm_mac Doesn't the V6 use RF to communicate with the flashes? If so, how can it support power control of any of these older models?
V6 units communicate with each other via RF. The don't directly communicate with a flash via RF (with the exception of the RF60 which has a built-in V6 receiver).
If you want to remote control the power of an older flash, you have to put it on to the hot-shoe of a V6 in receiver mode. This V6 receiver will then receive power and trigger instructions from another V6 in transmitter mode.
The V6 in receiver mode uses either the digital protocol of the flash (P-TTL in the case of Pentax) or the analogue TTL protocol that uses a so-called quench signal to control the flash duration and hence the flash power. Which protocol is used depends on the capabilities of the flash and what kind of V6 profile is available for it.
I hope that clarifies it.
P.S.: I will publish a V6 review in the near future. It will hopefully answer all typical questions.