18WuD2x

622 serrated rotor plate • sexadecimal number system
(e.g., the tracking of radio-frequency tuned
circuits in a radio receiver).
serrated vertical sync pulse In television, the vertical
sync pulse notched at twice the horizontal
sweep frequency.
service 1. To maintain or repair electronic equipment.
2. To provide maintenance or repair of electronic
equipment.
serviceability ratio For a device or system, the ratio
ts/(ts + td), where ts is serviceable (operational)
time, and td is downtime (non-operational
time).
serviceable time The cumulative time during
which an operator-monitored (but not necessarily
operated) device or system is capable of normal
operation.
service area For a broadcast or communications
station, the useful coverage area.
service band 1. For a communications system, the
band of frequencies in which operation is normally
carried out. 2. A band of frequencies specifically
assigned, by government regulation, to a
certain communications service or services.
service channel The band of frequencies that a
particular broadcast or communications station
occupies, when the carrier frequency is held constant.
service charge The amount charged by a technician
for installation, maintenance, or repair of
equipment. It is often performed on a per-hour
basis.
service maintenance For a cell or battery, the relative
amount of energy capacity (percentage of
full-charge capacity) available at a given time, or
after a certain length of time in normal use.
service meter 1. An energy (“power”) meter. Also
see KILOWATT-HOUR METER. 2. A rugged multimeter
used by a service technician.
service oscillator A signal generator designed expressly
for troubleshooting and repair service.
service switch 1. The main switch controlling the
electric service to a building or other place of installation.
2. In television repair, a switch on the
rear of a chassis. The switch facilitates adjustment
of screen controls by removing vertical deflection
temporarily.
service-type instrument An instrument having
reasonable accuracy and a degree of ruggedness
so that it is suitable for field or shop use.
Examples: SERVICE METER and SERVICE OS-
CILLATOR. Compare LABORATORY-GRADE
INSTRUMENT.
servo amplifier A highly stable amplifier designed
expressly for use in a SERVOMECHANISM.
servo loop In a control system (particularly a servo
amplifier), the output-to-input feedback loop,
through which automatic control is performed.
servomechanism Also called servo. A self-correcting,
closed-loop control system. It usually uses
an electromechanical device, such as a motor,
that controls some electronic device. Error signals,
supplied by the controlled electronic device,
cause the motor to run in such a way as to optimize
or stabilize the system.
servomotor A motor operated by the output signal
of a servo amplifier. Depending on the end application
of the servo system, the motor signal might
or might not be corrected.
servo oscillation In a servo system, a back-andforth
movement or fluctuation, relative to the
optimum setting or position. It Results from improper
system adjustment. Sometimes the system
stabilizes at the optimum after a short period
of oscillation; in some cases, the oscillation continues
indefinitely.
servo robot A (usually industrial) robot whose motion
sequence is programmed into a computer.
The robot follows the instructions given by the
computer, and makes precise, timed movements
on that basis. Different computer programs allow
different motion sequences, so a single robot can
be used for various tasks.
servo system An automatic control system using
one or more servomechanisms.
set
1. A piece of equipment or a system (e.g., radio
set). 2. In a flip-flop circuit, an input that is not
controlled by the clock. 3. To adjust a circuit or
device, such as a flip-flop, to a desired operating
point or condition. 4. A class of numbers, things,
or events. 5. In computer programming, to initialize
a variable (i.e., to assign a label to a location).
set analyzer A combination test instrument designed
originally for troubleshooting radio receivers.
It consists of a multimeter and transistor
tester or vacuum-tube tester.
set noise Electrical noise arising inside a radio or
television receiver, as opposed to that picked up
from the outside.
set pulse A pulse used to adjust a device to a certain
state (see SET, 3).
set terminal In a flip-flop, the one-input terminal.
Compare RESET TERMINAL.
setting The position or value to which an adjustable
device is set for a particular purpose.
settling time 1. In a digital voltmeter, the time required
between the application of a test voltage
and the final display of an accurate readout. 2. In
a digital-to-analog converter, the time between
half of the level change over all inputs and the arrival
of the output to a level within a certain tolerance
of its specified final level. It is defined for
either full-scale to zero or zero to full-scale.
set up To arrange and prepare equipment for operation.
setup See SET, 1.
set-up time 1. The time required to install and test
an electronic system, and to ready the system for
operation. 2. In a digital gate, the length of time
that a pulse must be held to produce a change of
state.
sexadecimal number system
NUMBER SYSTEM.
See HEXADECIMAL