AW: Early 1970's adventures (long winded post)

[Haible Juergen]

	>Wayne showed
	>me how the same thing could be done with any oscilloscope. Take
a sawtooth
	>signal (for example) and feed it into the external sweep (X)
input on a
	>scope. Put the output of a control voltage pedal into the
regular input
	>(Y). Place a high speed photo detector in front of the scope
screen, it
	>must be a photo transistor because a photoresistor is too slow.
Now invert
	>and amplify the output of the phototransistor. This makes the
output high,
	>when it goes dark.
	>
	>You can draw different shapes onto acetate with India ink and
tape them to
	>the screen with transparent tape. Take a drawing of a tree like
structure
	>that starts with a single line, splits, splits again and so
forth. With the
	>CV pedal at the bottom, the signal sweeps through a single
interruption and
	>outputs a single pulse per sweep. As you increase the control
voltage it
	>sweeps the two branches and outputs two pulses per sweep etc.
For such a
	>simple gadget it really has amazing capabilities as a
waveshaper.

Great Idea !

I think it would be a good thing to include a little o'scope into a
Modular
system anyway (though I don't have one integrated in mine yet), so it
would be great to have it for waveshape checking as well as waveshaping.

I guess the screen must have a black enclosure in front of it, maybe
with
a slit to insert the hand-drawn waveshaping masks ?

JH.