Normand Martel <[EMAIL PROTECTED]> wrote: > It was part of a Marconi (damn, i don't remember the > model number, but it was an OOOOOLD model), more > precisely the 600 MHz divide by ten prescaler. > > The input divider was based on two tunnel diodes that > acted as a div. by two divider followed by the really > most bizarre divide by five unit i ever saw: Fifteen > discrete NPN transistors arranged in a star (or > pentagon (Helloooo Echelon!! ) ) topology with the > input placed at the center of the star. The 15 > transistor were in a symmetrical loop of 5 three > transistor units working in a closed loop. > > Years later, i've made searches to find the schematic > of this prescaler, but without the model number, this > is quasi-impossible. > > If one of this forum's members has this schematic, i > would be pleased to ask for a copy!
I would make a very straightforward guess that the pentagon was simply a divide-by-five ring counter. Each shift register is two transistors... third transistor might be for clock buffering, or maybe (would require a slight break in symmetry) initialization to a known state? Too many people seem to neglect the ring counter and go straight to binary counters. Not sure if this is a defect of the educational materials replicated throughout the decades or what. The ring counter is not a one-trick-pony, instead it solves (AUTOMATICALLY) all the glitches encountered with decoding states from binary counters. Tim. _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
