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 ???

 

Hi,

Without any more deatails than those given, you'll have to rely on the old eyeball.

Electronic methods might include monitoring X/Y deflection voltages to look for similar projections, and even looking at beam current. It changes when passing over a glowing area - that's how the old memory tubes worked.