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From: tli@uscvax.UUCP (Tony Li)
Newsgroups: net.periphs
Subject: Re: terminal noise
Message-ID: <1257@uscvax.UUCP>
Date: Sat, 8-Dec-84 03:45:36 EST
Article-I.D.: uscvax.1257
Posted: Sat Dec  8 03:45:36 1984
Date-Received: Sun, 9-Dec-84 06:16:14 EST
References: <36@mot.UUCP>
Organization: CS&CE Depts, U.S.C., Los Angeles, CA
Lines: 30

> [Hic sunt dracones]
> 
There are NO dragons here.  Even if things do keep draggin' on. (Sorry, I
couldn't resist.)

> I am typing this at a Televideo 950 terminal and am listening to 
> a high-pitched continuous sound emanating from the terminal.
> It is near the upper limit of my hearing, maybe 15-17 kHz,
> and is loud enough to be distracting.  I mentioned this to someone else 
> and he said that all terminals do that.  Maybe his hearing is better 
> than mine, because I never heard it on any other terminal.  
> I seem to remember a letter to the editor of Byte magazine a year 
> or two ago complaining about the same thing. Can any of you hardware
> types explain this sound? Is it indeed universal? Are the makers of
> terminals aware of this and do they try to minimize it?  For me,
> this adds a new criterion for the selection of a terminal.
> 
This is the flyback transformer, and is a necessity for generating the HV
that your screen needs.  Yes, it is universal (for screens - get a plasma
display and you'll never hear it).  Minimization of the noise is usually by
selection of the type of transformer to use.  
> 
>                      Alan Filipski
>             {allegra | ihnp4 } ! sftig ! mot ! al
> 
-- 
Tony Li ;-)		Usc Computer Science
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