18WuD2x

P band • peak envelope power 519
P band A radio-frequency band extending from 225
to 390 MHz.
PBX Abbreviation of PRIVATE BRANCH EX-
CHANGE.
PC 1. Abbreviation of PERSONAL COMPUTER.
2. Abbreviation of PRINTED CIRCUIT. 3. Abbreviation
of PHOTOCELL. 4. Abbreviation of POSITIVE
COLUMN. 5. Abbreviation of POINT-CONTACT.
6. Abbreviation of PERCENT (also, pct.). 7. Abbreviation
of PROGRAM COUNTER.
pc 1. Abbreviation of PICOCOULOMB. Also, pC
(preferred). 2. Abbreviation of PICOCURIE. Also,
pCi (preferred). 3. Abbreviation of PARSEC.
pC Abbreviation for PICOCOULOMB.
PCB Abbreviation of PRINTED-CIRCUIT BOARD.
PC board See PRINTED-CIRCUIT BOARD.
PC diode See POINT-CONTACT DIODE.
p-channel JFET See P-CHANNEL JUNCTION
FIELD-EFFECT TRANSISTOR.
p-channel junction field-effect transistor Abbreviation,
PFET. A junction-type FET in which
the gate junction has been formed on a bar or
die of p-type semiconductor material. Compare
N-CHANNEL JUNCTION FIELD-EFFECT TRAN-
SISTOR.
p-channel MOSFET A metal-oxide semiconductor
field-effect transistor in which the channel is
composed of p-type silicon. Also see DEPLETION-
TYPE MOSFET, DEPLETION-ENHANCEMENT-
TYPE MOSFET, and ENHANCEMENT-TYPE
MOSFET.
pCi Symbol for PICOCURIE.
PCL Abbreviation of PRINTED-CIRCUIT LAMP.
PCM Abbreviation of PULSE-CODE MODULATION.
PCM-FM Pertaining to a carrier that is frequency
modulated by information that is pulse-code
modulated. Also see FREQUENCY MODULATION
and PULSE-CODE MODULATION.
PCM-FM-FM Pertaining to a carrier that is frequency
modulated by one or more subcarriers
that are frequency modulated by information that
is pulse-code modulated. Also see FREQUENCY
MODULATION and PULSE-CODE MODULATION.
PCM level In a pulse-code-modulated signal, one
of several different possible signal conditions.
PCM-PM Pulse-code modulation that is accomplished
by varying the phase of the carrier wave.
PC relay See PRINTED-CIRCUIT RELAY.
PCS Abbreviation for PERSONAL COMMUNICA-
TION SERVICE.
PC transistor See POINT-CONTACT TRANSISTOR.
PD 1. Abbreviation of PLATE DISSIPATION. 2. Abbreviation
of PULSE DURATION. 3. Abbreviation
of PROXIMITY DETECTOR. 4. Abbreviation of
POTENTIAL DIFFERENCE.
Pd Symbol for PALLADIUM.
PDA Abbreviation for personal digital assistant. See
HANDHELD COMPUTER.
PDAS Abbreviation of programmable data acquisition
system.
P display See PLAN POSITION INDICATOR.
PDM Abbreviation of PULSE-DURATION MODULA-
TION.
PDM-FM Pertaining to a carrier that is frequency
modulated by one or more subcarriers that are
frequency modulated by pulses that are pulseduration
modulated. Also see FREQUENCY
MODULATION and PULSE-DURATION MODULA-
TION.
PDM-FM-FM Pertaining to a carrier that is frequency
modulated by one or more subcarriers
that are frequency modulated by pulses that are
pulse-duration modulated. Also see FREQUENCY
MODULATION and PULSE-DURATION MODULA-
TION.
PDM-PM Pertaining to a carrier that is phase modulated
by pulse-duration-modulated information.
Also see PHASE MODULATION and PULSE-
DURATION MODULATION.
PDT Abbreviation of PACIFIC DAYLIGHT TIME.
PDVM Abbreviation of PRINTING DIGITAL VOLT-
METER.
PE 1. Abbreviation of POTENTIAL ENERGY. 2. Abbreviation
of PROFESSIONAL ENGINEER. 3. Abbreviation
of PROBABLE ERROR.
peak 1. The maximum value of a quantity. 2. In an
alternating-current cycle, the maximum positive
or negative current or voltage point. 3. The frequency
at which the transmission by a bandpass
circuit or device is maximum (attenuation is
minimum), evidenced by a maximum in the
frequency-response curve.
peak amplitude 1. The maximum positive or negative
current or voltage of a wave. 2. The maximum
instantaneous power of a signal.
peak anode (plate) current The maximum instantaneous
current flowing in the anode (plate) circuit
of a vacuum tube.
peak anode (plate) voltage The maximum instantaneous
voltage applied to the anode (plate) of a
vacuum tube.
peak chopper See PEAK CLIPPER.
peak current Abbreviation, I p . The highest value
reached by an alternating-current half-cycle or a
current pulse. Also called MAXIMUM CURRENT.
peak detector See PEAK PROBE.
peak distortion 1. The maximum instantaneous
distortion in a signal, generally expressed as a
percentage. 2. Distortion of a modulated signal at
envelope peaks.
peaked sawtooth A wave composed of a sawtooth
and peaking-pulse components. The deflection
voltage of a magnetic-deflection cathode-ray tube
requires this waveform to produce a current sawtooth
in the deflecting coils.
peaked waveform An alternating-current waveform
having nearly pointed positive and negative
half-cycles. Such a wave contains appreciable
third-harmonic energy.
peak envelope power Abbreviation, PEP. For a linear
radio-frequency (RF) power amplifier handling
a modulated signal, the average RF output