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From: ruck@sphere.UUCP (John R Ruckstuhl Jr)
Newsgroups: sci.electronics,misc.misc
Subject: Re: Re: Phone Harassment
Message-ID: <193@sphere.UUCP>
Date: 16 Mar 90 22:03:00 GMT
References: <21849@watdragon.waterloo.edu> <13746@watcgl.waterloo.edu> <AZzm_Iy00VoE46Oac6@andrew.cmu.edu>
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In article <AZzm_Iy00VoE46Oac6@andrew.cmu.edu>, wb1j+@andrew.cmu.edu (William M. Bumgarner) writes:
>al@gtx.com (Alan Filipski) writes:
>>In article <90071.220057SAB121@psuvm.psu.edu> SAB121@psuvm.psu.edu writes:
>>>
>>>There's an even more interesting version of that going around near where I
>>>lived. Get an air horn like the type used for small boats. Keep it handy by
>>>the phone. Next time the bastard calls, give him a shot of that. It's almost
>>>guarenteed that in 24 hrs or less he'll be stopping by an emergency room to
>>>get work done on his ruptured eardrum.
>> 
>Considering the rather low bandwidth of the phone signals and the way
>the system is designed, I would bet that a signal loud enough to
>actually cause serious ear damage would come through the line as
>mostly distortion....  a phone connection isn't just a microphone on
>one end w/ an amplifier on the other-- the switching equipment in
>between will define the limits as being far below that dangerous of a
>level.

Based on experiments conducted while I was a college freshman, I assert
that causing ear damage by the means discussed previously is not
possible.
There are several ways the large amplitude signal !might! be limited: 
I believe one or more are true. 
1.  The microphone saturates.
2.  The switcher at telephone central office has protective limiting
    and/or conditioning.
3.  If the signal is digitized to be transmitted between central
    office's, that digitization limits the signal. 
4.  The speaker saturates.
There is likely (but I don't know) a regulation (FCC?) on the signal 
levels output by one's telephone (to the central office).
Someone with test equipment at their desk might want to apply test
signals to their office-mate's telephone handset speaker to confirm or
contradict the theory of !speaker! saturation occuring below sound 
levels capable of causing pain.

I don't believe limiting is more conspicuous in poor-quality personal
telephone equipment.
-- 
John R Ruckstuhl, Jr	...!hplabs!hp-lsd!sphere!ruck