18WuD2x

216 dry pile • dual-cone speaker
dry pile A voltaic pile containing numerous disks
silvered or tinned on one face and covered with
manganese dioxide on the other.
dry reed A metal contact, generally used as a relay
or switch, that moves toward or away from another
fixed contact under the influence of a magnetic
field.
dry-reed relay See DRY-REED SWITCH.
dry-reed switch A switch consisting of two thin,
metallic strips (reeds) hermetically sealed in a
glass tube. The tube is surrounded by a coil of
wire. When a current flows in the coil, a magnetic
field affects the reeds. In the normally open dryreed
switch, the magnetic field causes the reeds
to come together and close the circuit. In the normally
closed dry-reed switch, the magnetic field
causes the reeds to separate, opening the circuit.
Compare MERCURY-WETTED REED RELAY.
dry run 1. The preliminary operation of equipment
for testing and appraisal. Such a procedure precedes
putting the equipment into regular service.
2. A step-by-step, paper-and-pencil “run” of a
computer program before it is machine-implemented.
dry shelf life The life of a battery cell stored without
its electrolyte.
dry-transfer process A method of transferring
printed-circuit patterns and panel labels from
sheets by rubbing them onto the substrate or
panel.
dry-type forced-air-cooled transformer A DRY-
TYPE TRANSFORMER that is cooled by convection
of air circulated by a blower or fan. This
increases the amount of power that the transformer
can safely handle.
dry-type self-cooled transformer A DRY-TYPE
TRANSFORMER that is cooled by natural air circulation
(convection), without the use of a blower
or fan.
dry-type transformer A transformer that, rather
than being immersed in oil, is cooled entirely by
the circulation of air.
DSB Abbreviation of DOUBLE SIDEBAND.
DSBSC Abbreviation of DOUBLE-SIDEBAND SUP-
PRESSED CARRIER. Also abbreviated DSSC.
dsc Abbreviation of double silk covered (wire).
D scope A radar whose display resembles that of a
C scope, the difference being that blip height
gives an approximation of the distance.
D service A Federal Aviation Agency service providing
radio broadcasts of weather data, notices
to aircraft personnel, and other advisory messages.
D-shell connector A multi-pin connector (either
male or female) with a characteristic shape that
ensures proper pin placement. Commonly used
for computer ports, and for connections of peripherals
to electronic equipment.
dsp Abbreviation of double silver plated.
DSR Abbreviation of DYNAMIC SPATIAL RECON-
STRUCTOR.
DSS Abbreviation of direct station selection (telephone).
DSSC Abbreviation of DOUBLE-SIDEBAND SUP-
PRESSED CARRIER. Also abbreviated DSBSC.
DT Abbreviation of DATA TRANSMISSION.
DTA Abbreviation of differential thermoanalysis.
DT-cut crystal A piezoelectric plate cut from a quartz
crystal at an angle of rotation about the z-axis of
–53 degrees. It has a zero temperature coefficient of
frequency at approximately 30 degrees Celsius.
Also see CRYSTAL AXES and CRYSTAL CUTS.
DTL Abbreviation of DIODE-TRANSISTOR LOGIC.
DTn Abbreviation of DOUBLE TINNED.
DTS 1. Abbreviation of DATA-TRANSMISSION SYS-
TEM. 2. Abbreviation of digital telemetry system.
DU Abbreviation of DUTY CYCLE.
dual 1. Pertaining to a combination of two components
such as diodes, transistors, etc., in a single
housing. The components are often carefully
matched. Compare QUAD. 2. Pertaining to a device
or circuit that behaves in a manner analogous
to that of another operating with component
and parameter counterparts. Thus, a current amplifier
can be the dual of a voltage amplifier;
a series-resonant circuit, the dual of a parallelresonant
circuit; or a field-effect transistor, the
dual of a bipolar transistor.
dual-beam CRT A cathode-ray tube having two
separate electron guns, for use in a dual-beam
oscilloscope.
dual-beam oscilloscope Also called dual-trace oscilloscope.
An oscilloscope having two electron
guns and deflection systems; it can display two
phenomena on the screen simultaneously for
comparison.
dual capacitor 1. Two fixed capacitors combined
in a single housing, sometimes sharing a common
capacitor plate. 2. A two-section, ganged
variable capacitor.
dual-channel amplifier An amplifier having two
separate, independent channels (e.g., a stereo
high-fidelity audio amplifier).
dual-cone speaker A speaker designed for a wide
range of audio frequencies. One cone responds to
the bass (low) and midrange audio frequencies,
and a smaller cone responds to the treble (high)
audio frequencies.