On Fri, 13 Oct 2000, Bob Ammerman wrote:

> If I were building something that:
>
> 1: I knew was going to be connected _only_ to a PC's serial port.
>
> 2: Was _very_ cost sensitive
>
> Then I might consider using the direct-TTL trick.

I dunno.  I looked at the specs for the 148x and MAX232 type line
receivers, and all of them I saw would see 0 and 3.5V as valid RS232
levels, at least as far as they were concerned.  It surprised me that even
the 1489(88? haven't used one in years) didn't need to see a negative
voltage.  I seem to recall the cutoff was 0.7V.  Has anyone had an actual
experience with something that would *not* work with the simple resistor
interface, I wonder?  I've had them talking to PCs, modems, and terminal
servers.

Dale
---
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
                -- Isaac Asimov

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