Thanks for the positive comments. It isn't perfect, as I explained, but like most things I put together, a limited budget predominates.
Fortunately - and probably like many members here - over the years I have accumulated a huge amount of electronic bits 'n' pieces etc., so it's quite satisfying to convert 'surplus stuff' into something useful. So for this project, very little specific expense was required. Plus, it's fun to be creative and to answer one's question "I have an idea; it looks like it will work - on paper, that is - so let's see . . ."
Al.