JAY EMRIE wrote in a message to AUGUST ABOLINS:

AA> JE> I have no idea what printer this is, but if it is a dot matrix, they
AA> JE> normally have an internal paper (activated switch)..

AA>There is a small curved piece of plastic that is mounted on a spring.  But
AA>there is NO WAY that this piece can be "depressed" unless
the paper is
 JE> flat-out
AA>taught and ready to print.   BTW... the ux177 is a fax machine.

 JE> I wasn't explicit enough when I said lasers, etc had a similar
 JE> setup. I should have elaborated: Many use a LED and sensor. When
 JE> the paper breaks the led beam the sensor recognizes this and
 JE> indicates to the printer (fax) that paper is present. Oft times the
 JE> sensor gets covered with paper dust and doesn't react to anything
 JE> -absence or presence of paper. 

I would think that if the sensor were blocked with dust or whatever,  it'd
act like the paper were there all the time,  rather than the other way
around.

Ever notice how seldom stuff gets designed with sensible failure modes?  :-)

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