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a remote control tester is it possible with this assembly?
Technically, yes. Of course you need to add a few things. Here is what you are describing - used commonly as an "end stop".

You need to hold the remote that you are testing right up to the unit, trying to hit the detector. It should be able to tell you whether "something" is coming out of the remote.
You would be able to tell more (like distance) using one of these.

But, remotes are typically encoded, not just a presence or absence / on or off. These are fun and very cheap kits that, along with a controller, you can play with.

If you have a time machine, you can go pick up one of these at the Shack

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