how can i detect when a signal overlaps other on a CRO scree

how can i know whether a signal has overlapped on other on a C.R.O.

for eg. i want to know whether a circle has overlapped on a semicircle on a C.R.O

actually my circuit will make a circle move continuously on the C.R.O screen . and a user will be moving a semicircle thru his control keys horizontally and vertically.how can i know when these two touch each other ???

How do you do that? Do you have two chopped inputs?

by using analog multiplexer

i do it by an analog multiplexer with a counter( of very high clock speed ) connected to its selection lines. so they appear to be at the same time though they r not so. i think this reply should be sufficient for Mr. electronicsgod

Way to go myturn. That attitude is exactly how I would want to make friends and influence enemies.
Your chances of any meaningfull answer just dropped to the same probability as a welcome reception for a cockroach at a formal dinner party.
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