18WuD2x

transverse electric mode • triangulation 693
transverse electric mode In a waveguide, the condition
in which the electric lines of flux are perpendicular
to the direction of propagation.
Compare TRANSVERSE MAGNETIC MODE. Also
see WAVEGUIDE MODE.
transverse electromagnetic wave An electromagnetic
wave having electric-field vectors and magnetic-field
vectors perpendicular to the direction
of propagation.
transverse magnetic mode In a waveguide, the
condition in which the magnetic lines of flux are
perpendicular to the direction of propagation.
Compare TRANSVERSE ELECTRIC MODE. Also
see WAVEGUIDE MODE.
trap 1. See WAVETRAP. 2. In a semiconductor
crystal, an imperfection capable of trapping current
carriers.
trapezoid 1. A polygon having four sides, of which
only two are parallel. 2. See TRAPEZOIDAL PAT-
TERN. 3. See TRAPEZOIDAL WAVE.
trapezoidal distortion In television or facsimile, a
form of distortion in which the frame is wider at
the top than at the bottom, or vice versa.
Top of screen
Bottom of screen
trapezoidal distortion
trapezoidal pattern An oscilloscope pattern used
to check the percentage of modulation of an amplitude-modulated
wave. Its name is derived from
its trapezoidal shape.
trapezoidal wave A nonsinusoidal wave that is a
combination of a rectangular component and a
sawtooth component. It is the required waveform
of the voltage applied to a magnetic deflecting coil
(oscilloscope or television) to ensure a sawtooth
wave of current in the coil.
traveling-wave amplifier Abbreviation, TWA. An
amplifier based on the unique operation of the
traveling-wave tube.
traveling-wave tube Abbreviation, TWT. A microwave
tube containing an electron gun, helical
transmission line, collector, and input and output
couplers. A microwave signal is coupled into
the helix, through which it travels while the gun
projects an electron beam through the helix.
x
Modulation (%) = 100 ( x − y ) x + y
trapezoidal pattern
When wave and electron velocities are equal, a
power gain is obtained in the signal coupled out
of the helix. Also see BACKWARD-WAVE OSCIL-
LATOR.
Travis discriminator A discriminator circuit in
which the diodes are operated from separately
tuned halves of the secondary winding of the input
transformer. Compare FOSTER-SEELEY
DISCRIMINATOR.
treasure locator See METAL LOCATOR.
treble The higher portion of the sound spectrum—
especially the upper end of the musical scale
(middle C and above). Compare BASS.
treble boost 1. Amplification of high audio frequencies
(the treble notes) in an audio system—
especially in high-fidelity music reproduction.
2. The extent of amplification of high audio
frequencies in audio applications—especially in
music reproduction. 3. A control that allows
adjustment of the relative treble gain in an audio
system.
treble control See TREBLE BOOST, 3.
tree 1. A cause-and-effect chain with two or more
independent branches. 2. A circuit with two or
more branches but no meshes.
TRF Abbreviation of tuned radio frequency.
TRF amplifier See TUNED RADIO-FREQUENCY
AMPLIFIER.
TRF receiver See TUNED RADIO-FREQUENCY
RECEIVER.
triac A three-terminal, gate-controlled, semiconductor
switching device. Compare DIAC.
triangular wave See BACK-TO-BACK SAWTOOTH.
triangulation A method of radiolocation in which
directional bearings are obtained for the signals
from two transmitters whose positions are
accurately known. The position of the receiver is
indicated by the intersection of two lines on a
y