So that means the motion rate of the picture gets divided down by 3 giving a less fluid more jerkier motion picture? Reminds me of those Cartrivision VCRs I read about which used a compression system of recording only every 3rd field
http://www.labguysworld.com/Museum017.htm , a demo of this machine in action can be seen here
http://www.youtube.com/watch?v=CPEjhiOk2XI on the game show "What's My Line" 1972.
Have to say initially before reading up on the Col-R-Tel article on the Early Television Foundation website I thought the B&W set scanning rate was modified to 180 fields/sec and the NTSC signal gets chopped into sequential fields to reproduce a 30 frame/sec NTSC picture through the wheel. Now that would be a good experiment for technological minded TV enthusiasts to try out hey