Thu Feb 14 Gavin Melville wrote:
...
As the OP who started this discussion I appreciate all the comments.
The original spec was not to invent new components, but to use things
you could actually get in 1900. Just because I know how to make
an IC
now doesn't mean I could have made one in 1900. While I could have
obtained Silicon, it's unlikely it would have been usable purity, and
the imaging, etching and depositation would be simply impossible.
The "was it available" we have looked hardest at is the transistor,
and
could have we made a point contact transistor then, even a FET (made
before the transistor but didn't recognise it). While we might be
able
to do this, we're trying to limit our search to things we could get,
rather than make, or materials we could get rather than make ie iron
cores, as opposed to point contact transistors. ( We are, however
keeping an eye on the 256 2n2222 project).
...
As an option for I/O, you might consider a Nipkow (pronounced 'Nip-
kov') disk as a mechanical video display unit. Nipkow disks were
well known in 1900, and several television designs had been proposed
by then (and some of them even had much, much more than a snowball's
chance of working).
Another thing you might consider is to use a nickel coating on the
disk; with suitable read & write heads you could build a sort of bit-
mapped video memory. Poulsen had demonstrated magnetic recording in
1898, and it was used in some early Marconi equipment as a detector.
A sensitive mirror galvanometer connected to the read head would
modulate your light source behind the scanning disk. You need to
write the appropriate bit images to the tracks, but assuming the disk
spins at about 1500 RPM, you only need modulate at audio frequencies
to produce usable video; you could use a carbon amplifier (as used by
the phone company at that time) to drive each write head.
Another thing magnetic recording might do for you is as a source of
higher frequencies: prerecord at slow disk RPM, read at much higher RPM.
-Bobby