Analogue vision mixers need all their sources to be genlocked - that is, the signals must all be synchronised - in order to work. In 2000, YSTV's Panasonic F10 cameras had genlock capability and so did the [Amiga], but everything else (VT machines, the Mac edit suite, graphics computers, etc) needed to go through a framestore synchroniser. At that time, we had a single P164 that could act as a framestore synchroniser, but this was rather limiting as it meant we could only handle one non-genlocked source at a time. Michael Prior-Jones bought a dual-channel framestore second-hand (found on the uk.tech.broadcast newsgroup, I think...) and this gave us the capability to handle three sources into the Cox T8 vision mixer.
The framestore also had a little remote control panel which could be used to do cuts and fades between the two channels, which led us to use it once or twice as a self-contained OB vision path. It became largely redundant with the coming of Magic DaVE.