Steven Swift wrote:
Greetings.

A short while ago, I posted a request for links to simple triggered
sweeps for older recurrent timebase oscilloscopes. I spent a fair
amount of time looking in old magazines and circuit handbooks, but
didn't find what I thought I was looking for.

So I decided to cobble-up a homebrew of my own. This circuit probably
has been done before, but it met my criterion of being really simple.
I used already on-hand parts, so the design is far from optimum. It
works fine on an Eico 460 up to about 1MHz. No attempt was made to make
a calibrated sweep. You could use a 5v rail and an HC4538 to make a
nice high speed triggered sweep.

Have a look at:

http://novatech-instr.com/Fun/trig.pdf

Thank you to all of you who sent me emails and posted comments on these
boards.

Steve.
Seattle,WA.

I think you could use an LM361 comparator in place of the front opamp.
It produces high going and low going digital outputs that you can
enable separately, so you can choose whether you want to sync on
positive going or negative going edges, without changing the switching
threshold.

It will also clock the flip flop a lot faster than an opamp will.

http://www.national.com/ds.cgi/LM/LM161.pdf