18WuD2x

protective resistor • pseudo-instruction 559
To
antenna
Protective
gaps
Two-wire
feed line
protective gap
Tuning
network
protective resistor 1. A bleeder resistor connected
in parallel with a filter capacitor in a high-voltage
direct-current power supply to discharge the capacitor
automatically, thus preventing electric
shock. 2. A series resistor that limits the current
going through a device.
+
Protective
resistor
protective resistor, 2.
protector 1. A fast-acting power-disconnect device,
such as a circuit breaker or fuse, that acts to
protect electronic equipment. 2. A device or connection,
such as a safety ground or ground-fault
interrupter, that protects an operator from electric
shock. 3. See CONTACT PROTECTOR.
protium The light isotope of hydrogen, having an
atomic mass of 1.
protoactinium See PROTACTINIUM.
protocol 1. A set of parameters for a digital communications
signal. 2. The method by which a
procedure is followed; a uniform set of governing
regulations. It ensures proper operation of a system
or network.
+
proton A positively charged particle in the nucleus
of an atom. The mass of a proton is approximately
1840 times the mass of an electron.
proton rest mass See MASS OF PROTON AT
REST.
proton-synchrotron A synchrotron that uses frequency
modulation of the radio-frequency accelerating
voltage. It can accelerate protons to
energies of several billion electronvolts.
prototype The preliminary design or model of a device
or system. It is often modified numerous
times before the final design is attained. Compare
PILOT MODEL.
proustite Crystalline silver arsenide trisulfide. Artificial
crystals of this compound are used in tunable
infrared-ray instruments.
proximity alarm A capacitance relay used to actuate
an alerting-signal device when an area is intruded
upon or a person is too close to a
protected object. Also called INTRUSION ALARM.
proximity detector See PROXIMITY SENSOR.
proximity effect 1. The influence of highfrequency
current flowing in one conductor on
the distribution of current flowing in an adjacent
conductor. 2. In an audio system, the result of
placing a microphone too close to a person’s
mouth. Under these conditions, some spoken
consonants (e.g., B, F, P, and T) produce clapping
or booming sounds.
proximity fuse An electronic device situated in the
nose of a missile. When the missile is near the
target, the fuse transmits a signal that is reflected
back from the target; this reflected signal detonates
the missile.
proximity relay See CAPACITANCE RELAY.
proximity sensing The ability of a machine, especially
a robot, to detect when an object is near.
This is an aid in robot navigation because it prevents
collisions. Some devices can measure the
distance from a robot, or from a robotic end effector,
to a nearby object.
proximity sensor A device that indicates the presence
of a nearby body. Such a device uses some
form of circuit, such as that of a CAPACITANCE
RELAY, that changes its operating characteristics
when an object enters its field.
proximity switch See CAPACITANCE RELAY.
PRR Abbreviation of PULSE REPETITION RATE.
PRV Abbreviation of PEAK REVERSE VOLTAGE.
PS Abbreviation of POWER SUPPLY.
ps Abbreviation of PICOSECOND. (Also, psec.)
PSD Abbreviation of PHASE-SENSITIVE DETEC-
TOR.
psec Abbreviation of PICOSECOND. (Also, ps.)
pseudocode In a computer system, an instruction
or code symbol that affects the operation of the
programming in an indirect manner.
pseudo-instruction In computer programming operations,
data representing an instruction and requiring
translation by a compiler or assembler.