What Use Is An F-call?

What use is an F-call? When I was a lad, which for me was in the 1970's, I had a big tub of LEGO. I used it to learn about the mechanics of things. I built a diff with Yellow, Blue and Red cogs - long before LEGO Technic came along with a pre-made diff. I built trucks and steering linkages, suspension arms and when I had the opportunity to build a V8 engine with several kits from friends, I did that. My electronics building followed a similar path. I had a Commodore VIC-20 - which reminds me, Jack Tramiel, the founder of Commodore Business Machines passed away aged 83 - read up on his story when you have a moment. Anyway, I had a Commodore VIC-20. My experimentation with that was at a TTL level, rather than at a component level. I plugged in switches and connectors, made a serial port between an Apple ][ and my VIC-20 and did all manner of software and hardware experiments. Other amateurs I have spoken with have experienced a similar journey, some with LEGO, others with Meccano, or Valves, Leiden Jars or a