18WuD2x

phasing capacitor • phonetic alphabet 527
phasing capacitor In a crystal filter, a small variable
capacitor that constitutes one arm of a
four-arm bridge in which the crystal is another
arm. Adjustment of this capacitor balances the
bridge, thus preventing the undesirable passage
of a signal through the capacitance of the crystal
holder.
phenol-formaldehyde plastics A family of plastic
insulating materials made with phenolic resin,
and occasionally used as dielectrics and air-core
coil forms. Some of the trade names for these materials
include Bakelite, Catalin, Durez, Durite,
Formica, and Micarta.
phenolic insulants See PHENOL-FORMALDE-
HYDE PLASTICS.
phenolic resin A synthetic resin made by condensing
phenol (carbolic acid) with formaldehyde.
phenomenon An event or circumstance that can
be verified by the senses, as opposed to one subject
to theory or speculation (e.g., the phenomenon
of magnetic attraction).
Phillips gate A device that allows measurement of
the gas pressure in a confined chamber. A current
is passed through the gas. The magnitude of
the current, for a given gas, is a function of the
gas pressure and temperature.
Phillips screw A screw with a pair of slots in its
head. The slots are arranged like an x. Phillips
screws are available in many different sizes, as are
ordinary screws. The x-shaped pair of slots reduces
the tendency for the screwdriver to slip out
of the screw head as the screw is rotated.
Phi phenomenon The illusion of motion resulting
from the rapid presentation to the eye of pictures
showing objects in a succession of different positions.
Television and motion pictures exploit this
illusion. Also see PERSISTENCE.
pH meter An instrument used to measure the
acidity or alkalinity of solutions. Also see PH, 1.
phon A unit of apparent change in loudness discerned
by a listener. Unlike the decibel, the phon
includes compensation for the ear’s nonlinear response
to attendant frequency changes. At a frequency
of 1 kHz, a change in loudness of 1 phon
is the equivalent of 1 decibel.
phone 1. Telephone (wire or radio). 2. To establish
communication via telephone. 3. Colloquialism
for voice communication (radiotelephone), particularly
via amateur-radio single sideband on the
high-frequency bands (160 through 10 meters).
4. A minimal, unique speech sound. Also called
SOUND UNIT.
phoneme An individual sound or syllable in the
human voice, with a characteristic amplitude-vs.
frequency spectral pattern. It is important in
speech recognition and speech synthesis. Computers
can be programmed to identify and transcribe
these sounds; computers can also be
programmed to generate the sounds from text
data.
phone jack The female mating device for a PHONE
PLUG.
phone monitor A simple device for listening to
amplitude-modulated radio transmissions to
test their quality. In its most rudimentary form,
it consists of a pickup antenna, semiconductor-diode
detector, and high-resistance headphones.
phone patch A device for establishing a connection
(patch) between radio and wire-telephone facilities.
Also see PATCH.
phone plug A type of plug originally designed for
patching telephone circuits, now widely used in
electronics and instrumentation. In its conventional
form, it has a rod-shaped neck that
serves as one contact, and a ball on the tip of
the neck, but insulated from it, that serves as
the other contact. Typical diameters are 1 ⁄8 inch
and 1 ⁄4 inch.
phone test set An instrument for checking the
performance of a radiotelephone transmitter. The
set combines the functions of field-strength meter,
modulation indicator, and aural monitor.
Sometimes it includes a volt-ohm-milliammeter
for troubleshooting the transmitter.
phonetic alphabet Words whose initial letters are
used to identify the letters of the alphabet for