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From: Finney@ssc-vax.UUCP (Ken Finney)
Newsgroups: net.micro
Subject: RS232 Voltages
Message-ID: <55@ssc-vax.UUCP>
Date: Fri, 19-Jul-85 18:01:48 EDT
Article-I.D.: ssc-vax.55
Posted: Fri Jul 19 18:01:48 1985
Date-Received: Sun, 21-Jul-85 23:55:02 EDT
Distribution: net
Organization: Boeing Aerospace Co., Seattle, WA
Lines: 13

The official voltages levels are +12 and -12, giving
an awful lot of noise margin.  To save money, microcomputers
years ago started using +5 and 0.  I have seen a lot of
peripherals that clip the incoming voltages to +4.7 and
0.7 using a zener and a resistor.  These peripherals work
whether you are using the official voltages or not.


		-Ken Finney-
		@Boeing Aerospace  


"I know the world is hollow, for I have touched the sky."