Don McKenzie wrote:

> I recall the 33/66 ms timing was done with a set of brass wings in a
> small cup that acted as a govenor. You adjusted it so a zero produced
> an even 1 second timing.

  Actually, you adjusted it with the meter, which I have somewhere in
my collection (Boy, I hope I took the batteries out some time in the
last 10 years!).  It goes without saying that the mark-space ratio was
indicated on a normal meter movement, adjusted to FSD on mark (which is
of course what you have already with the dial at rest).

  The pulse rate however is read from a frequency meter of the reed-comb
variety, about seven reeds.  We have a couple of these of various types,
including the one to show mains frequency, a bigger version (much) of
those you see on up-market petrol alternators.  We used this to
demonstrate the generation of sidebands from (amplitude) modulation
using a mechanical rotary sinewave modulator (curious Heath-Robinson
construction using rotary switch and hand-made wirewound resistors).

  It works!

  Cheers,
        Paul B.