Hi Tony,

> Any idea how long is this sequence Can you notice it repeat when

using high frequency clocks

Personally, no I can't, at least it is not obvious to me in the way
that some sequences I've heard are. At high clock rates (say knob
setting below about 3, so above a couple of kilohertz or so) it
sounds pretty much like white noise, and so I find becomes harder to
hear any 'structure' that one can latch onto and see if it repeats.
And of course at slower rates, you have to listen for that much
longer to see if the 'structure' one can hear *does* repeat.

The circuit uses all 18 stages available in the '4006 chip used
(which has 2 blocks of 5 bits, and 2 blocks of 4 bits), but the way
the feedback is accomplished, I doubt the sequence is 2^18 long: 2
bits are XORed, then inverted (ensures some 1s injected which
prevents the sequence being all 0s), then this is XORed to a third
bit, which is then fed back. From memory I think this is likely to
mean that the 'linear complexity' of the sequence will be less than
18, which means it could be generated on a shorter shify register
(assuming the tap-points were available). Alas it is some years since
I studied such things, as otherwise I could probably have worked out
the appropriate polynomial and *told* you how long the sequence is...!

Tim