> I basically understand rs232 voltage levels but there remains one
> ambiguity.  If voltages in the range of +-3 volts are undefined, are
> signals that fluctuate from -10 to +0.18 volts safely ignored?  I have a
> circuit that uses the idle receive current to feed the negative transmit
> level.  Yes, I can store the charge in a capacitor but I want to be
> cheap.  The result of eliminating the cap is the incomming rs232 signal
> is echoed out but at levels of -10 to +0.18 and it seems to work.  But
> will it work *all* the time?  Is this within specs?

        I am not sure but no, I doubt it will always work. "undefined" means "never
go there", each implementation might result in completely contradictory
results. I have seen many RRS232 circuits rely on the fact that they act as
expected to TTL levels, but I have also found a few ports that don't respond
well to TTL levels. If this is just a hobby project then go for it, but if
this is a product then I'd be more wary on going this route. TTYL

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