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Re: RS232 Voltage Levels

On Fri, 06 Jan 2006 18:36:03 GMT, Jonathan Kirwan

> Gave us: > >>>> >>>>>> >>>[snip] >>> >>>> There may still be some devices that will convert RS-232 levels to >>>>TTL and some that go the other way. >>> >>>RS-232 -> TTL = MC1489 >>> >>>TTL -> RS-232 = MC1488 >>> >>>These chips are still available more than 40 years after I designed >>>them ;-) >>> >>>These chips adhere to the original RS-232 spec. >>> >> >>1488 requiring several supplies -- and runs hot as a pistol, too. I've >>got a box of both; they were about all there was to use in the market >>and worked well when I was using them; but don't use them much now >>because of the power requirements (especially the 1488) and the >>serious heat to be removed (again the 1488 much more than the 1489, if >>memory serves, but neither of them slouches in the heating >>department.) >> > > Sounds like a poorly implemented utilization. Sum Ting Wong must > have done the design.

They always worked well for me - and everyone else in the industry for about 20 years...

Bob

Reply to
Bob Stephens
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The RS-232 specification was originally designed as an interface for electro-mechanical printers, using discrete transistor logic to convert signals coming over telephone pair hooked up to the old relay-switched public telephone system into successive ASCII characters printed on a rol of paper.

Search on "Telex" and "TWX". It up-graded the original 50/75 character-per-second telex system whose only active components were electro-mechanical - essentially relay logic.

You should be able to find a history of the ASR-33 terminal somewhere on the web - that was the cheap version of the ASR-35 bought by people who had to handle significant amounts of TWX traffic.

--
Bill Sloman, Nijmegen
Reply to
bill.sloman

What is "Fuchs"? Shorthand for f*ck-head? I plonked him weeks ago. I recommend everyone else do the same.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
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I love to cook with wine.      Sometimes I even put it in the food.
Reply to
Jim Thompson

German word for "FOX"

-- Uwe Bonnes snipped-for-privacy@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt

--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

Reply to
Uwe Bonnes

Nope. The ASR-33 was 20 mA current loop - not RS232.

Bob

Reply to
Bob Stephens

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