VLVL2(3): Early-Warning Alarm

[Dave Monroe]

   "'So, let me guess, I'm spoze to be some
early-warning alarm, some invisible beam she can walk
through and break, so you get a few minutes' edge but
meanwhile I'm the one gets interrupted, or come to
think of it, broken, somethin' like that?'" (VL, Ch.
3, p. 30)


"early-warning alarm"

http://www.lswilson.ca/dewmap.jpg

http://www.lswilson.ca/dewhist-a.htm

http://www.lswilson.ca/dewline.htm#A

>From Manuel De Landa, War in the Age of Intelligent
Machines (New York: Zone, 1991) ...

"Understanding the nature of a citadel under siege,
and the accompanying logistics and organization, is
essential to understanding what happens to a nation
when the old fortress walls are extended through radar
to contintental proportions." (p. 5)

And see as well ...

http://home.i1.net/~bytor/dew.html

http://www.lyricscafe.com/r/rush/058.htm?lyricscafe=ef29637ff6a7d534f91745bdc7d5602c


"invisible beam"

photoelectric cell 
  
or photocell, device whose electrical characteristics
(e.g., current, voltage, or resistance) vary when
light is incident upon it. The most common type
consists of two electrodes separated by a
light-sensitive semiconductor material. A battery or
other voltage source connected to the electrodes sets
up a current even in the absence of light; when light
strikes the semiconductor section of the photocell,
the current in the circuit increases by an amount
proportional to the intensity of the light. In the
phototube, an older type of photocell, two electrodes
are enclosed in a glass tube—an anode and a
light-sensitive cathode, i.e., a metal that emits
electrons in accordance with the photoelectric effect.
Although the phototube itself is now obsolete, the
principle survives in the photomultiplier tube, which
can be used to detect and amplify faint amounts of
light. In this tube, electrons ejected from a
photosensitive cathode by light are attracted toward
and strike a positive electrode, liberating showers of
secondary electrons; these are drawn to a more
positive electrode, producing yet more secondary
electrons—and so on, through several stages, until a
large pulse of current is produced. Besides its use in
measuring light intensity, a photomultiplier can be
built into a television camera tube, making it
sensitive enough to pick up the visual image of a star
too faint to be seen by the human eye. The
photovoltaic type of photoelectric cell, when exposed
to light, can generate and support an electric current
without being attached to any external voltage source.
Such a cell usually consists of a semiconductor
crystal with two zones composed of dissimilar
materials. When light shines on the crystal, a voltage
is set up across the junction between the two zones. A
phototransistor, which is a type of photovoltaic cell,
can generate a small current that acts like the input
current in a conventional transistor and controls a
larger current in the output circuit. Photovoltaic
cells are also used to make solar batteries (see solar
cell). Since the current from a photocell can easily
be used to operate switches or relays, it is often
used in light-actuated counters, automatic door
openers, and intrusion alarms. Photocells in such
devices are popularly known as electric eyes. 

http://www.bartleby.com/65/ph/photelcel.html

And see as well ...

http://hypertextbook.com/physics/modern/photoelectric/index.shtml

http://www.nobel.se/physics/laureates/1921/

Not to mention ...

http://home.nc.rr.com/tuco/looney/acme/electric.html

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