This is a 240V unit with PAL output.
These machines contain an OS ROM that selects one of a number of programs in paged ROM to boot into. Most machines destined for general purpose use would boot into BBC BASIC. As the machine found many uses beyond BASIC programming (word processing, terminal emulation for example), the default boot environment could be changed.
This unit was equipped with an Intel 8271 floppy disk controller device. These did not ship with the base model by default, so the disk option must have been installed at one time. The 8271 is said to have been obsolete before Acorn even used them in the design of the BBC Model B. Later units have a 1770 controller. A couple of days before the event I burned a copy of Acorn DFS 0.98 which is compatible with the 8271.
Incidentally, the Utility ROM slot of the BBC uses the 27128 device pinout. 27256s *may* work but I decided not to take the chance. A standard 34-pin floppy flatform cable connects to the floppy disk connector on the underside of the board and a DSDD drive was configured as Drive 1.
When you bought the DFS option, you'd have received the controller chip, ROM, and a utility disk containing programs for formatting diskettes. In the absence of the utility disk, I used a short BASIC program, keyed in, to format a diskette. The BBC treats each side of the diskette as a separate disk unit, unit 0 being side 1 of the first drive, unit 2 being side 2 of the first drive. If you try this at home don't forget to format both sides of your disk if you're using a double-sided drive. I had no problems formatting DSDD diskettes on the 8271 with Acorn DFS 0.98.
The screen shot below shows the output from the *CAT command on the drive with a newly formatted diskette in place.