In telegraphy an instrument for repeating the signals through a second
line. It is virtually a relay which is operated by the sender, and which
in turn operates the rest of the main line, being situated itself at
about the middle point of the distance covered. In the simpler forms of
repeater two relays are used, one for transmission in one direction the
other for transmission in the other. An attendant switches one or the
other in as required.

Thus a common relay is virtually a repeater for its local circuit. If
such a relay is placed half way down a line, and if the line beyond it
is connected as its local, it becomes a repeater.

Some forms of repeaters are automatic, and repeat both ways without the
need of an attendant.

It is the practice to somewhat prolong the signals sent through a
repeater.

In a system of plane co-ordinates (see Co-ordinates) the
distance of any point from the axis of ordinates measured parallel to
the axis of abscissas.

In the cut the abscissa of the point a is the line or distance a c.

Fig. 1. AXES OF CO-ORDINATES

In medical electricity, the region surrounding the electrode applied to
the human body.

In medical electricity, the region surrounding the polar zone, q. v.

An apparatus used in telegraphy for sending a momentary reverse current
into the line after each signal, thus counteracting retardation.

The terminal connecting with the zinc plate, or its equivalent in an
electric circuit; the negative electrode; the kathode. A term now little
used.

A metal; one of the elements; atomic weight, 65.1;
specific gravity, 6.8 to 7.2.

microhms.
Resistance at 0° C. (32° F.), per centimeter cube,   5.626
Resistance at 0° C. (32° F.), per inch cube,         2.215

Relative resistance (silver = 1),                    3.741

ohms.
Resistance of a wire, 1 foot long, weighing 1 grain,   .5766
(a) 1 foot long, 1 millimeter diameter,            33.85
(b) 1 meter long, weighing 1 gram,                   .4023
(c) 1 meter long, 1 millimeter diameter,             .07163

Zinc is principally used in electrical work as the positive plate in
voltaic batteries.

There are three thermometric zeros. In the Réaumur and centigrade
scales, it is at the temperature of melting ice; in the Fahrenheit
scale, it is 32° F. below that temperature, or corresponds to -17.78° C.

The third is the absolute zero. (See Zero, Absolute.)

Conventionally, the potential of the earth. True zero potential could only exist in the surface of a body infinitely distant from other electrified bodies.

From several considerations it is believed that at a certain temperature
the molecules of all bodies would touch each other, their kinetic motion
would cease, and there would be no heat. This temperature is the
absolute zero. It is put at -273° C. (-459° F.)

[Transcriber's note; The modern value is 0° Kelvin,  -273.15° C, or
-459.67° F. The lowest reported temperature observed is 1E-10° K.]