By far the cheapest of the 3 and because of that, the most sold one. The machine, also known as the Trash 80, was modified a lot by consumer. The main cause was the shop where these were sold, the Radio Shack shops.
By default, the machine (keyboard only) no controller for floppy, printer or serial interface. These could be bought separately as an Expansion Interface which is below the monitor. The monitor is essentially a TV without tuner.