Cable Hanger Tongs.
Tongs for attaching cable hangers, q.v. They have long handles so as to
be worked from the ground at the middle of a span.
Cable, Suspending Wire of.
A wire by which an aerial cable is in part or entirely suspended. The
cable, being incapable of sustaining its own weight, is secured by clips
or hangers to a wire, strong from pole to pole immediately above it.
(See Cable Hanger.)
Cable Tank.
A tank in which a submarine cable is coiled away on board a cable-laying
ship, or in the factory on shore for the purpose of testing or
watching its insulation. Sometimes, in order to test it under pressures
approximating to those it will be subjected to in practice, the tank is
closed and the portion of cable within it is subjected to hydraulic
pressure. This represents the pressure it will be exposed to in deep
water.
Calamine.
A mineral; zinc silicate; formula Zn2 Si 03, crystalline system,
Orthorhombic; specific gravity, 3.16-3.9.
The crystals often show strong pyroelectric properties.
Calibration.
The determination by experiment or calculation of the value of the
readings of an instrument, such as a galvanometer or eudiometer. Thus if
a tangent galvanometer has its circle graduated in degrees, a table of
the value of tangents corresponding to every reading occurring in
practice would represent a calibration by calculation. A determination
of the current required to produce each deflection would be a
calibration in the more usual sense. Calibration is generally absolute,
as referring to some fixed unit, but it may be relative, as between two
things both of unknown absolute value.
Calibration, Absolute.
The determination of the absolute value of currents producing given
deflections in a galvanometer, or in other instruments the determination
of corresponding values, as the instrument may be a magnetometer,
quadrant electrometer, or other apparatus.
Calibration, Invariable.
Calibration applicable to specially constructed galvanometers, which is
unaffected by the proximity of masses of iron or field magnets. Such
galvanometers must have a constant controlling field. Such is given by a
powerful permanent magnet, whose field is practically unaffected by the
causes named. Or else, in place of a controlling field, a spring maybe
used to which the needle is attached, and which tends to hold it in one
position.