Extension Bell Call.
A system of relay connection, q. v., by which a bell is made to continue
ringing after the current has ceased coming over the main line. It is
designed to prolong the alarm given by a magneto call bell, q. v., which
latter only rings as long as the magneto handle is turned. A vibrating
electric bell (see Bell, Electric,) is connected in circuit with a local
battery and a switch normally open, but so constructed as to close the
circuit when a current is passed and continue to do so indefinitely. The
distant circuit is connected to this switch. When the magneto is worked
it acts upon the switch, closes the local battery circuit and leaves it
closed, while the bell goes on ringing until the battery is exhausted or
the switch is opened by hand.
Eye, Electro-magnetic.
An apparatus used in exploring a field of electro-magnetic radiations.
It is a piece of copper wire 2 millimeters (.08 inch) in diameter, bent
into an almost complete circle 70 millimeters (.28 inch) in diameter,
with terminals separated by an air gap. This is moved about in the
region under examination, and by the production of a spark indicates the
locality of the loops or venters in systems of stationary waves.
F.
Abbreviation for Fahrenheit, as 10º F., meaning 10º Fahrenheit. (See
Fahrenheit Scale.)
Fahrenheit Scale.
A thermometer scale in use in the United States and England. On this
scale the temperature of melting ice is 32°; that of condensing steam is
212°; the degrees are all of equal length. Its use is indicated by the
letter F., as 180° F. To convert its readings into centigrade, subtract
32 and multiply by 5/9. (b) To convert centigrade into F. multiply by
9/5 and add 32. Thus 180° F. = ((180-32) * 5/9)° C. = 82.2° C. Again
180° C. = (180 * 9/5) + 32 = 324° F.
[Transcribers note: 180° C. = (180 * 9/5) + 32 = 356° F. ]
The additions and subtractions must be algebraic in all cases. Thus when
the degrees are minus or below zero the rules for conversion might be
put thus: To convert degrees F. below zero into centigrade to the number
of degrees F. add 32, multiply by 5/9 and place a minus sign (-) before
it. (b) To convert degrees centigrade below zero into Fahrenheit,
multiply the number of degrees by 9/5, subtract from 32 if smaller; if
greater than 32 subtract 32 therefrom, and prefix a minus sign, thus:
-10° C. = 32 - (10 * 9/5) = 14°. Again, -30°C. = (30 * 9/5) - 32 = 22 =
-22° F.