18WuD2x

mercury delay line • meson 441
mercury delay line A delay line in which delay is
obtained by propagating the signal through a
pipe of mercury.
mercury diffusion pump A vacuum diffusion
pump using mercury vapor.
mercury displacement relay A form of switching
relay in which the electrical contact is made by
moving mercury.
mercury-jet switch A multipoint switch using a jet
of mercury instead of the conventional wiper arm,
for high-speed operation and reduced wear.
mercury memory A recirculating memory using a
mercury delay line. Also see DELAY LINE and
DELAY-LINE MEMORY.
mercury-pool cathode In certain industrial electron
tubes, such as the ignitron, a cathode electrode
consisting of a pool of mercury.
mercury-pool rectifier A type of mercury-arc rectifier
whose cathode is a pool of mercury. In one
type, the arc is initiated by tilting the tube momentarily
to bring the mercury into contact with
a third electrode, thus causing a starting current
to flow through the pool. In another type, the ignitron,
a starter electrode is in continual contact
with the mercury.
mercury pump See MERCURY DIFFUSION PUMP.
mercury rectifier See MERCURY-POOL RECTI-
FIER and MERCURY-VAPOR RECTIFIER.
mercury relay A relay in which at least one of the
contacts is mercury.
mercury storage See MERCURY MEMORY.
mercury switch A switch consisting essentially of
two or more stiff wire electrodes and a drop of
mercury hermetically sealed in a glass tube. Tilting
the tube causes the mercury to flow toward
one end, where it immerses the electrodes, providing
a conductive path between them.
mercury-vapor lamp A glow lamp emitting bluegreen
light that causes ionization of mercury vapor
by an electric current.
mercury-vapor rectifier A tube-type high-voltage
diode rectifier containing a small amount of mercury
that vaporizes and ionizes during tube operation.
mercury-vapor tube 1. See MERCURY-VAPOR
LAMP. 2. See MERCURY-VAPOR RECTIFIER.
mercury-wetted reed relay A reed relay in which
the reeds are wetted with mercury in a pool by
capillary action. The film of mercury forms a tiny
bridge when the reeds open; when this bridge separates,
a clean, high-speed break occurs without
contact bounce. Compare DRY-REED SWITCH.
merge 1. In computer operations, to make a single
set or file from two or more record sets. 2. In word
processing, to create a corrected master recording
from two input media: the original master
recording and the recording that contains the
corrections.
meridian 1. A great circle passing through earth’s
geographic poles and a given point on the surface
of the earth. 2. A line of longitude on a map or
globe. Also see TIME ZONE, ZERO MERIDIAN,
and ZONE TIME.
mesa A flat-topped, protruding region in a semiconductor
wafer. The mesa is produced by etching
the surrounding part of the material. Some
bipolar transistors are manufactured in this way.
mesa diffusion A method of manufacturing bipolar
transistors. The different semiconductor materials
are first diffused together. Then part of the
resulting wafer is etched away, resulting in a
mesa shape.
mesa transistor A diffused planar transistor in
which the silicon area around the base has been
etched away to reduce collector-to-base capacitance;
the base-emitter region remains elevated
like a high plateau (mesa).
Emitter
Alloyed
region
Base
mesa transistor
Diffused region
Collector
Semiconductor
MESFET A form of field-effect transistor combining
depletion-mode and enhancement-mode properties.
A Schottky barrier forms the gate electrode.
mesh 1. A combination of the elements that form a
closed path in a network. 2. The closed figure
(such as the delta or star) obtained by connecting
polyphase windings together. 3. A grid, screen, or
similar structure in a vacuum tube.
mesh equations Equations describing fully the
current and voltage relations in a network of
meshes (see MESH, 1).
Mesny circuit A push-pull ultra-high-frequency
(UHF) oscillator whose gate or base tank is a pair
of parallel wires short-circuited by a slider; the
drain or collector tank is a similar pair of wires.
The frequency is varied by moving the sliders
along the wires.
mesochronous A condition for signals in which
significant instants pass at identical average
speeds, such as bits per second.
meson An unstable nuclear particle first observed
in cosmic rays. A meson can be electrically positive,
negative, or neutral. Its mass lies between
that of the electron and proton.