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Posting-Version: version B 2.10.2 9/18/84; site persci.UUCP
Path: utzoo!linus!decvax!tektronix!uw-beaver!tikal!cholula!persci!bill
From: bill@persci.UUCP
Newsgroups: net.micro
Subject: Re: servo computer products
Message-ID: <246@persci.UUCP>
Date: Fri, 19-Jul-85 10:37:14 EDT
Article-I.D.: persci.246
Posted: Fri Jul 19 10:37:14 1985
Date-Received: Sun, 21-Jul-85 04:19:57 EDT
References: <732@abnji.UUCP> <7000006@uicsl>
Reply-To: bill@persci.UUCP (Bill Swan)
Organization: Personal Scientific, Woodinville WA
Lines: 14
Summary: 

In article <7000006@uicsl> pollack@uicsl.UUCP writes:
>Does anybody know how to get an RS232 interface off a board with
>only a +5 power supply? I thought -12 was needed...
>Jordan

To build a proper interface, you do. The RS-232 spec says that you should
drive the lines between +/- 5V (minimum). In practice, most RS-232 receivers
have a threshold of about 1 volt, which means that in a pinch you could drive
the line with TTL directly. Not a great practice, but it (usually) works.

Otherwise, you need to provide -12V, which can be done with a DC-DC converter.

-- 
Bill Swan 	{ihnp4,decvax,allegra,...}!uw-beaver!tikal!persci!bill