The Standard Electrical Dictionary Part 3

An appliance for calling attention, generally by ringing a bell. It is used to notify of water-level in boilers or tanks, of entrance of a house, or of other things as desired. It is evident that any number of alarms could be contrived.

18 STANDARD ELECTRICAL DICTIONARY.

Alarm, Fire and Heat.

An alarm for giving notice of the existence of a conflagration. Such are sometimes operated by a compound bar thermostat (see Thermostat), which on a given elevation of temperature closes a circuit and rings an electric bell. Sometimes the expansion of a column of mercury when heated is used. This, by coming in contact with one or two platinum points, completes a circuit, and rings the bell.

The identical apparatus may be used in living rooms, greenhouses.

factories and elsewhere, to give an alarm when the temperature rises or falls beyond predetermined limits.

Alarm, Overflow.

An alarm to indicate an overflow of water has been suggested on the lines of a contact completed by water, or of the elements of a battery which would be made active by water. Thus two sheets of metal might be separated by bibulous paper charged with salt. If these sheets were terminals of a circuit including a bell and battery, when water reached them the circuit would be closed and the bell would ring. It was also proposed to use one copper and one zinc sheet so as to const.i.tute a battery in itself, to be thrown into action by moisture. These contacts or inactive batteries could be distributed where water from an overflow would be most likely to reach them.

Alarm, Water Level.

An alarm operated by a change of water level in a tank or boiler. By a float a contact is made as it rises with the water. Another float may be arranged to fall and close a contact as the level falls. The closing of the contacts rings an electric bell to notify the attendant in charge.

Alcohol, Electrical Rectification of.

A current of electricity pa.s.sed through impure alcohol between zinc electrodes is found to improve its quality. This it does by decomposing the water present. The nascent hydrogen combines with the aldehydes, converting them into alcohols while the oxygen combines with the zinc electrode.

Alignment.

The placing in or occupying of the same straight line. The bearings of a shaft in dynamos, engines, and other machinery have to be in accurate alignment.

Allotropy.

The power of existing in several modifications possessed by some substances, notably by chemical elements. Instances of the allotropic state are found in carbon which exists as charcoal, as graphite (plumbago or black lead), and as the diamond. All three are the same elemental substance, although differing in every physical and electrical property.

19 STANDARD ELECTRICAL DICTIONARY.

Alloy.

A mixture, produced almost universally by fusion, of two or more metals.

Sometimes alloys seem to be chemical compounds, as shown by their having generally a melting point lower than the average of those of their const.i.tuents. An alloy of a metal with mercury is termed an amalgam. An important application in electricity is the use of fusible alloys for fire alarms or for safety fuses. German silver is also of importance for resistance coils, and palladium alloys are used for unmagnetizable watches. An alloy of wrought iron with manganese is almost unmagnetizable, and has been proposed for use in s.h.i.+p building to avoid errors of the compa.s.s.

Alloys or what are practically such can be deposited by electrolysis in the electro- plater's bath. We give the composition of some alloys interesting to the electrician.

Solder: Lead 1 part Tin 2 parts " " " 1 "

" " " 2 "

German Silver: Copper, 2 parts; Nickel, 1 part; Zinc, 1 part (used for resistances).

Platinum, Silver Alloys: Platinum, 1 part; silver, 2 parts (used for resistances.)

Palladium alloys for watch springs. (See Palladium.)

Alphabet, Telegraphic.

The combinations of sounds, of dots and dashes marked on paper, of right-hand and left-hand deflections of a needle, of bells of different notes, or of other symbols by which a fixed combination is expressed for each character of the alphabet, for numerals, and for punctuation. While the code is designed for telegraphic uses it can be used not only for the conveyance of signals and messages by the electrical telegraphs, but also by any semaphoric or visual system, as by flashes of light, movements of a flag or even of the arms of the person signalling.

In the English and continental needle telegraphy in which the message is transmitted by the movements of an index normally vertical, but oscillating to one side or the other under the influence of the current, the latter being controlled by the transmitter of the message, the left hand swings of the needle are interpreted as dots, the right hand as dashes.

This system enables one alphabet to be translated into the other, or virtually one alphabet answers for both Morse and needle transmitters.

There are two princ.i.p.al telegraphic alphabets, the American Morse and the International codes. They are very similar, their essential distinction being that s.p.a.ces are used in the American code, while they are excluded from the International code.

In the American Morse system the message is now universally received by sound. (See Sounder--Sound Reading.)

20 STANDARD ELECTRICAL DICTIONARY.

The two codes or telegraphic alphabets are given here.

THE INTERNATIONAL ALPHABET.

Parenthesis, - . - - . - Understand, ... - .

I don't understand, ..-- ....--..

Wait, .-. . .

Erase, ... ... ...

Call signal, -.-.-.- End of message, .-.-.-.

Cleared out all right, .-..-..-.

A .- L .-.. W .-- B -... M -- X -..- C -.-. N -. Y -.-- D -.. O --- Z --..

E . P .--.

F ..-. Q --.- Ch ---- G --. R .-. ? .-.- H .... S ... ? ---.

I .. T - ? ..-- J .--- U ..- ? ..-..

K -.- V ...- ? --.--

NUMERALS 1 .---- 4 ....- 8 ---..

2 ..--- 5 ..... 9 ----.

3 ...-- 6 -.... 0 ----- 7 --...

[Transcriber's note: The original image of the dot/dash pattern is somewhat ambiguous. Since there may be differences from contemporary specifications, the original image is included.]

[Image of page 20: THE INTERNATIONAL ALPHABET.]

21 STANDARD ELECTRICAL DICTIONARY.

PUNCTUATION, ETC.,

Period (.) ... ...

Comma (,) .-.-.- Query(?) ..--..

Exclamation (!) --..-- Apostrophe (') .----.

Hyphen (-) -....- Fresh paragraph, .-.-..