battery, which
while it initially receives a charge of electricity,
is nevertheless, of such a character, owing to the
active material of which it is made, that it
accumulates, or, as it were, generates electricity.

Aerial Wire, The wire which, in wireless telegraphy, is carried
or Conductor. up into the air to connect the antennae with the
receiving and sending apparatus.

Alarm, Burglar. A circulating system in a building, connected up with
a bell or other signaling means.

Alloy. A mixture of two or more metals; as copper and zinc
to make brass; nickel and zinc to form German silver.

Alternating Current. A current which goes back and forth in opposite
directions, unlike a direct current which flows
continuously in one direction over a wire.

Alternation. The term applied to a change in the direction of an
alternating current, the frequency of the alternations
ranging up to 20,000 or more vibrations per second.

Amber. A resin, yellow in color, which when rubbed with a
cloth, becomes excited and gives forth negative
electricity.

Ammeter. An instrument for measuring the quantity or flow of
electricity.

Ampere. The unit of current; the term in which strength of
the current is measured. An ampere is an
electromotive force of one volt through a resistance
of one ohm.

Annunciator. A device which indicates or signals a call given from
some distant point.

Anode. The positive terminal in a conducting circuit, like
the terminal of the carbon plate in a battery. It is
a plate in an electroplating bath from which the
current goes over to the cathode or negative plate or
terminal.

Arc. A term employed to designate the gap, or the current
which flows across between the conductors, like the
space between the two carbons of an arc lamp, which
gives the light.

Armature. A body of iron, or other suitable metal, which is in