Date   : Thu, 18 Jul 2013 18:15:04 +0100
From   : chris@... (Chris Johns)
Subject: bbc-micro Digest, Vol 82, Issue 5

On 18/07/2013 18:04, Wookie wrote:

> 10*MOTOR 1
> 20*MOTOR 0
> 30GOTO10
>
> It makes an 'orrible sound.

We (as kids) thought it sounded a bit motorbike-like, and if you pressed 
a key it changed a bit (due to the processing of the key slowing the 
system down a bit).

> One of my first hardware things I did was to wire a 6V battery and bike
> headlight across the cassette relay and then wrote a program to flash it
> on and off in morse code.
>
> Then I wired up a light dependant resister across the joystick port on
> my plus1 and used that electron to read the morse code and show it on
> the screen.

I did something similar at college to connect two BBC Bs, using 
ultrasound (we had just built ultrasound sounders and receivers as part 
of the course).

You type a message on one computer and it used the motor relay (or maybe 
a user port line) to pulse the sound generation hardware. The listening 
end was wired to the analogue port. I think it used a really basic 
serial protocol, something on for a time, off the same time, then just 
timing to decode the 7 data bits.

Nearby dogs probably got a copy of the message too :)

Cheers

Chris