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This article was posted to the Usenet group alt.hackers in 1995; any technical information is probably outdated.

Re: Hacker FAQ (please comment and help fix)

Article: 7624 of alt.hackers
Newsgroups: alt.hackers
From: (Gavin Sallery)
Subject: Re: Hacker FAQ (please comment and help fix)
Sender: (Usenet Administration)
Organization: Demon Internet (news)
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Date: Sat, 8 Apr 1995 11:49:21 GMT
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Status: RO

> ObAsAKidIThoughtItWasCoolHack:
> Old TRS-80 Model I, with Expansion Interface.  (Man, just SAYING that
> takes me back...)  The EI had two cassette ports, that had a relay that
> audibly switched between them.  I worked out what address to POKE to in
> BASIC to do the switching, and made a neat little buzzer by switching at
> some atrociously fast rate.  I was just working out timing loops to play
> different notes when my Dad came in and got a bit peeved that I was
> wearing out the relay...

Did the same thing with a BBC model 'B' (with 64k 'sideways' RAM expansion...
but that's another story (basically, it paged memory addresses above 32k
between the expansion RAM, expansion ROM, and the OS (as far as I
remember))). The computer had a tape interface, along with a relay to control
the tape motor (wired to the same port socket on the tape recorder as those
foot-switches you get with desktop dictation machines). The relay was quite
easy to operate with an OS call, which you could put in a loop in about three
lines of BASIC. Made some very wierd noises that way.

On the same computer, making a *really* crufty sound-to-light effects device;
taking the tape output (analogue) to the RS423 input to produce a sort of
1-bit DAC (but slow :-)  ). The value read out of the RS423 interface at
regular intervals would cause different colours to be written to the screen.
Of course, it was far too random to look good, but fun nevertheless (when
you're 13!).

 ______  _________
/__     (_        \ Hertfordshire, England
\_|avin __)allery  \______________________
... Flash Gordon exposed himself to all sorts of danger.

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