Evan Weaver asked:
     Hello:

     I have a few questions. Some don't relate directly to PICs, but relate to
     my exploits with the same, and cause of the phenomal response to the "two's
     complement" question I thought someone might be kind enough to help me.

     1) PICs inputs/outputs are all TTL except for a few shmitt triggers in
     weird places, right?

The inputs work pretty much like TTL, but the outputs are more like high current
CMOS since they are driven rail-to-rail, not just to 2.4V like TTL. Outputs can
typically source 20mA and sink 25mA, but there is a total chip drive of 50 or
100mA, depending on the actual device used.

     2) Is there somekind of simple circuit or IC that converts a varying
     voltage to a current? I need this to use with a DAC that outputs voltage
     and I want to drive a speaker from it.  I am reasonable sure that most
     normal speakers run on varying current.

Sorry, you'll need to give us more info on this one - speakers are usually
driven by a voltage source, not a current source. I think all you'll need to do
is feed the DAC output to an audio amplifier, but if you give us more info we
can be more helpful.

     3) Could someone please explain negative voltage? I am confused.

Again, I'm not sure what you are asking here. The simple answer it that -ve
voltage is any voltage that is -ve WITH RESPECT TO CIRCUIT GROUND. If you can be
more specific I can maybe be more helpful.

CIAO - Martin Green