As far as I understood by "tension" you meant "напряжение"
![Smilie](https://forum.armkb.com/images/smilies/smile.gif)
Should've used word "voltage" or "current".
If my guess is right, then you could alter
the voltage by setting bits (LPT is outputing)
a unsigned byte and each tick. So, 01010101
for example. The voltage will be logical 1 and
logical 0 (no voltage and voltage). To control
the voltage more gradually, you should create
resister array, putting different ohm-age resisters, e.g. lower ohm on high bits, higher
ohmage on low bits. Connect all those resisters
on the other end, and take the ground as the
second wire. Now try writing a program which
increases and outputs a byte from 0 to 255
attach voltmeter and watch the read-out.
You have built your own DAC (Digital to Analog Converter). Congratulations.
By the way, years ago, when there were no
sound blasters out yet, there was a beast called
COVOX.
![Smilie](https://forum.armkb.com/images/smilies/smile.gif)
8bit mono sound device.
Have a look here if puzzled:
http://kiarchive.relcom.ru/pub/msdos...soundcard/dac/