Re; What to look for in a Model 33 Teletype - a newb's buyer's guide?

drlegendre . drlegendre at
Fri Nov 21 15:20:25 CST 2014

Tony & All,

On Fri, Nov 21, 2014 at 2:59 PM, tony duell <ard at> wrote:

> I suspect that most, if not all, of those RS232-TTL converters are just
> a MAX232 + the necessary capacitors, or something very similar.

The one I linked to seems to actually use an Atmel microcontroller that's
emulating the MAX232.. else I don't know why there would need to be a uC
chip on the board.

I mean to say, the MAX232 is effectively a one-chip 232 to TTL converter
solution, eh? Why would they need a micro to supplement it?

> Of course I've not tried it but I can see no reason why it wouldn't work.
> On the other hand, I can see no reason not to just buy the MAX232 chip,
> since you'll have to mount and solder up the optoisolators and associated
> components anyway.
> Yeah, pretty much. I went ahead and ordered 5pcs from Tayda Electronics
(via eBay). $2.29 including shipping..

Now about the optos.. do we really +need+ to use the HCPL 4100/4200 for
this application? Wouldn't other, more generic optos serve the same roles?
I realize that the 4100/4200 are high-performance parts, designed to handle
relatively high data rates - but at only 110 baud, I'd think just about any
opto with adequate light / dark resistances would be OK.

Then again, I've never played with this stuff.. might be completely wrong.
But I ask, as I already have a bunch of optos sitting in a drawer. ;-)

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