18WuD2x

406 life test • light-induced electricity
life test An assessment of the life of electronic
equipment—either by means of full-time test
runs or accelerated time tests.
lifetime See CARRIER LIFETIME.
lifter A device in a magnetic tape recorder that
removes the tape from the recording and playback
heads under fast-forward and rewind conditions.
light Visible electromagnetic radiation occurring in
the wavelength band of about 750 nanometers
(red light) to 390 nanometers (violet light). Included
sometimes in the category of light are infrared
and ultraviolet rays.
light-activated silicon-controlled rectifier Abbreviation,
LASCR. A silicon-controlled rectifier
that functions both as a photosensor and a heavyduty
bistable electronic switch, allowing high currents
to be switched by means of a light beam.
light-activated silicon-controlled switch Abbreviation,
LASCS. A pnpn device that acts simultaneously
as photocell and electronic switch.
light adaption 1. The process whereby the eye adjusts
itself to an increase or decrease in illumination.
2. Similar action in photoelectric devices.
3. The length of time required for the eye to adjust
itself to an increase or decrease in illumination.
light amplifier A solid-state amplifier using an input
electroluminescent cell and an output photocell,
or some similar pair of components. The
device is essentially an optoelectronic coupler
with gain.
light-beam communication A system of communication
in which a beam of light between transmitting
and receiving stations is modulated or
interrupted to convey intelligence. A laser is commonly
used because it has minimal beam divergence,
allowing maximum communication range.
light-beam meter An electric meter using a
LIGHT-BEAM POINTER.
light-beam pointer A slender beam of light that replaces
the pointer in a moving-coil meter. The
light comes from a small incandescent lamp and
is reflected by a mirror attached to the coil; when
the coil moves, a spot of light moves over the scale
of the meter.
light-beam receiver The receiver in a LIGHT-
BEAM COMMUNICATION system.
light-beam recorder A graphic recorder using a
light-beam pointer. In this device, a small spot of
light traces a pattern on moving photographic
film, which is subsequently developed to produce
a permanent record.
light-beam transmitter The transmitter in a
LIGHT-BEAM COMMUNICATION system.
light cable A cable, consisting of numerous thin
optical fibers, through which light can be transmitted
for communication or control purposes.
See, for example, LIGHT-WAVE TELEPHONY.
light chopper A device that modulates a light
beam by interrupting it repetitively.
Terminal
Modulated
light
beam
Photocell
Modem
Telescope
(for focusing light beam)
Modem
light-beam communication
Terminal
Laser
light detection and ranging Acronym, lidar. A
navigation and surveillance system in which laser
light scans in a manner similar to that of RADAR.
light dimmer See DIMMER.
lighted pushbutton See LIGHTED SWITCH.
lighted switch A pushbutton switch containing a
pilot light that glows to show when the switch is
on. Also called illuminated switch.
light-emitting diode Abbreviation, LED. A semiconductor
device that emits visible light when forward
biased. Also see LASER DIODE.
light-emitting film A thin phosphor film that
becomes luminescent when a high-frequency
voltage is applied across its surface. Also see
ELECTROLUMINESCENCE and ELECTROLUMI-
NESCENT CELL.
light flasher An electronic circuit or simple automatic
flasher switch for flashing a lamp at regular
intervals.
light flicker See LOAD FLICKER.
light flux See LUMINOUS FLUX.
light hood See HOOD.
light-induced electricity See PHOTOELECTRIC-
ITY.