🚀 go-pugleaf

I want to leave a XT with 30Mb hard disk available for public access, and still
preserve the data on it.  I proposed a five-position keyed switch with the
following positions:

  R.  All of 0 below applies, and the reset line to the XT is activated.
       The key springs to position 0.

  0.  All of I below applies, and the keyboard lock on the machine is
       enabled.

  I.  Hard disk is not powered up on startup, however, if the key is moved
       from position II, the HD is not powed down.  In that case, all write
       and read access to the HD is blocked.

  II. All write access to the hard drive is blocked.

  III.  All read and write access to the drive is permitted.

The key is removable from all of the positions except R.

My proposal received one reply which I foolishly misplaced, of how the
write line to the disk can be shorted to high by a audio jack.  However,
for some controllers the machine will not boot up in that case.