building my own relay computer

Tom Sparks tom_a_sparks at
Sat Feb 14 17:38:31 CST 2015

On 15/02/15 01:37, Peter Corlett wrote:
> On Fri, Feb 13, 2015 at 06:14:53PM -0700, ben wrote:
> [...]
>> 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.)
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

> 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


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