18WuD2x

402 L carrier • lead frame
L carrier In a telephone system, a carrier having a
frequency between approximately 68 kHz and 10
MHz. It can be used in wire-transmission or radio
links.
L C band A section of the L BAND extending from
465 MHz to 510 MHz.
LC bridge See INDUCTANCE-CAPACITANCE
BRIDGE.
LC constant Abbreviation, LC. The product of the
inductance and capacitance required for resonance
at a given frequency.
LCD Abbreviation of LIQUID-CRYSTAL DISPLAY.
LC filter See INDUCTANCE-CAPACITANCE FIL-
TER.
L circuit See L NETWORK.
LC meter See INDUCTANCE-CAPACITANCE ME-
TER.
LCR See INDUCTANCE-CAPACITANCE-RESIS-
TANCE.
LC ratio In a tuned circuit, the ratio of inductance
to capacitance.
LCR bridge See IMPEDANCE BRIDGE, 1.
L d Symbol for DISTRIBUTED INDUCTANCE.
LDF See LOW-FREQUENCY DIRECTION FINDER.
L display Also called L scan. A radar display in
which the target appears as two horizontal
traces, one extending from a vertical timebase to
the right, the other to the left.
lead Pronunciation, leed. 1. A conductor (usually
a wire) leading to or emerging from a terminal or
electrode. 2. In computations relating phase, the
extent to which one quantity precedes another
(e.g., current leads voltage by 90 degrees in a
pure capacitance). Compare LAG.
lead Pronunciation, led. Symbol, Pb. A heavy
metallic element. Atomic number, 82. Atomic
weight, 207.2. It can be used as a shield against
atomic radiation, and has various applications in
electronics (e.g., as electrodes in batteries and as
a component of solder). See LEAD-ACID BAT-
TERY, FUSE, and SOLDER.
lead–acid battery A set of two or more lead–acid
cells connected in series, usually housed in a
common enclosure. Some batteries of this type,
notably automotive batteries, are made from sets
of lead–acid cells having a free-flowing liquid acid.
Other cells have a semisolid “paste” electrolyte.
These batteries are popular in consumer electronic
devices that require a moderate amount of
current. They are also used in uninterruptible
power supplies (UPSs) for personal computers.
See LEAD–ACID CELL.
lead–acid cell A rechargeable electrochemical cell
having an electrolyte of sulfuric acid. The electrodes
are lead (negative) and lead dioxide (positive).
Produces about 1.5 volts under no-load
conditions when fully charged. A large cell of this
type can store several tens of ampere-hours.
Smaller units have less capacity but more versatility.
Their main advantage is reasonable cost,
considering that they can be charged and discharged
many times.
Strap
Positive
plate
Slotted rubber
separator
Wood
separator
Terminal
Bottom of
positive plate
Filler cap and vent
Sealing compound
Cover
Rubber
container
Negative
plate
Bottom
of
negative
plate
Supports
Sediment spaces
lead-acid cell
lead cell 1. A lead-acid cell. 2. A lead-sulfide photocell;
see LEAD SULFIDE, 1.
lead dress See DRESS.
leader 1. The blank section at the beginning of a
magnetic tape. It is usually made of plastic. 2. A
record, preceding a group of records, that identifies
the group and provides other data pertinent
to the group. 3. In a lightning stroke, the initial
movement of electrons or positive ions, creating
the ionized path that allows discharge.
lead frame The metal frame holding the leads
of a circuit package (DIP) in place before
encapsulation.