14 Feb
2015
14 Feb
'15
3:38 p.m.
On 15/02/15 01:37, Peter Corlett wrote:
On Fri, Feb 13, 2015 at 06:14:53PM -0700, ben wrote:
[...]
also magnetic wire
recording (1898) witch lead to magnetic tape
recording in 1940
in my "What If" world the postal office network owned the telegraph network
letters were delivered on punched card/tape to the post offices
places that had mail/post rooms were asked to rent a mail computer
THIS is that computer that I am concepting
The alu has never relay been a problem with
relays, but what about main
storage? Punched tape (paper/film/card) is no longer with us for I/O.
How about audio tones, as was popular in the eighties?
That is the *eighteen*-eighties! The "harmonic telegraph" was a new
development
in that decade. The principle was that it multiplexed different Morse streams
onto a single audio channel by using a different tone for each, and the
demultiplexing at the far end was done using a tuning forks which resonated at
the appropriate frequencies to close a circuit. (At this point it was
immediately realised that the sound source could be a human voice rather than
Morse keys, rendering the telegraph instantly obsolete.)
However, relay computers are more a 1940s technology, so one has the benefit of
valves in which one could implement a notch fiter and/or PLL to demodulate the
audio. Which period would you like to be appropriate to? :)
The other side of this is actually recording and replaying the audio. For
1880s, you're looking at wax cylinders, gramophones and whatnot, but we'd
pretty much figured out recording audio on magnetic tape by the 1940s. Compact
cassettes are from 1963, but I figure that if Zusie can use blue LEDs (1993,
and still expensive into the 2000s!) an old 1980s tape deck is fair game.
that why I asked about Magnetic tape filesystem and found phi-deck
I thought about record sized floppy disk :)
as I stepping stone I looked a normal floppy disk, but the are track
based not spiral based, CDs would add to much extra hardware, so
Magnetic tapes were the simpler option
tom