Telephone transmitter

“ In the case of the detectaphone transmitter, it only replaces the regular telephone transmitter and its presence will never be suspected. It operates just as well when the receiver is hung up as when it is off the hook, as far as the purpose I have in mind is concerned, as you shall see soon. I have put both forms in so that even if they find the one back of the tires, even the most suspicious person would not think that anything was contained in the telephone itself. We are dealing with clever people and two anchors to windward are better than one. ”

“ By connecting a telephone transmitter to the arc in the same manner that it is connected to the speaking arc, the oscillations can be varied in accordance with the vibrations of the voice. The apparatus is connected to the aerial and the earth through the medium of a loose-coupled helix, formed by providing the helix in series with the arc and condenser, with a secondary winding.
FIG. 148.—The Majorana wireless telephone transmitter.
The ordinary carbon transmitter, in its common form, is unsuited for wireless telephonic work, on account of its inability to handle large amounts of power. ”

“ Each of two persons, wearing dry shoes or rubber-soled slippers, grasps the terminal of one wire in one hand. The other hand is placed flat against the ear of a third person, with a piece of dry linen paper intervening between the hands and the head. If a fourth person, in the room where the induction coil is located, then closes the small switch and speaks into the telephone transmitter, the person against whose ears the hands are being held will hear the speech very distinctly. The ticking of a watch held against the mouthpiece of the transmitter will be heard with startling clearness. ”

“ The distance that can be covered with a wireless telephone transmitter is about one-fourth as great as that of a wireless telegraph transmitter having the same input of initial current, but it is long enough to satisfy the most enthusiastic amateur. ”

“ The Fuller cell was once largely used for supplying current to telephone transmitters at subscribers' stations, where very heavy service was demanded, but the advent of the so-called common-battery systems, in some cases, and of the high-resistance transmitter, in other cases, has caused a great lessening in its use. This is fortunate as the cell is a "dirty" one to handle and is expensive to maintain. ”

“ CARBON-DUST TRANSMITTER
The strength of current required for the telephone is very small. To transmit a telephone message requires less than a hundred-millionth part of the current required for a telegraphic message. The work done in lifting the telephone receiver a distance of one foot, if changed into an alternating current, would be sufficient to keep up a sound in the receiver for a hundred thousand years. Because of its extreme sensitiveness the telephone requires a complete wire circuit. The earth cannot be used for the return circuit, as in the case of the telegraph. ”

“ A brief description of the progress of a call from its institution to the complete connection and subsequent disconnection begins with the adjustment of the dial indicators of the telephone set and the turning of the crank of the signal transmitter one revolution. This act, performed by the calling subscriber, connects one of the line conductors to earth. Immediately the decimal indicator associated with the section in which the calling line terminates is energized and starts the division starter. The division starter instantly starts the rotary switch of an idle division. ”

“ The mechanism of the transmitter is complicated and cannot be described except scientifically. Its use allows one to talk long distances, even to the extent of 2,000 miles. Non-technically speaking, then, the telephone consists of a magnet, insulated wire, and a disc, the vibration upon the disc being transmitted over the wire from the sending to the receiving station, electricity being used for conveying the vibrations or sound. ”

“ Popularly speaking, it may be said that the transmitter takes the varying sounds of the human voice, and passes them on to the telephone wire, to be borne along thereon by the undulatory electric current until they reach the receiver, which takes and passes them to the human ear. ”

“ In order that an operator may have both hands free to manipulate the plugs, her telephone receiver is fixed over one ear by a fastening passing over her head, and the transmitter is hung from her shoulders so as to be close to her mouth.
In telegraphy it is the rule to employ the earth for the return part of the circuit, but this is not customary in telephony. The telephone is a much more sensitive instrument than the telegraph, and a telephone having an earth return is subject to all kinds of strange and weird noises which greatly interfere with conversation. ”

“ When used in connection with his articulating transmitter, which was developed at a later date, articulate words have been received upon it; and when a duplicate of the instrument is inserted in a closed circuit, which includes a galvanic battery, it becomes a speaking telephone capable of acting both as a transmitter and as a receiver. Mr. Gray did not know at that time, however, that he could use it as a transmitter, although he had fully demonstrated its ability to receive sounds of varying quality. ”

“ The transmitter, as above described, is in the square box, and its round black diaphragm may be seen behind the round hole into which one talks. [28] The receiver is the trumpet-shaped tube which hangs on its side, and is taken from its hook to be used. The call-bell has nothing to do with the telephone. It is operated by a small magneto-generator,--a very near relative of the dynamo-the current from which is sent over the telephone circuit (the same wires) when the small crank is turned. ”

“ Then, in August, 1877, Graham Bell showed the advantage of twisting 'the direct and return wires around one another, so they should be absolutely equidistant from the disturbing wires' in order to neutralize the effect of the inductive current and eliminate the noise.
Many experiments were made to invent an improved transmitter that would overcome the inductive effect and yet retain the marvelous simplicity of the hand telephone, with its entailed low cost of maintenance. ”

“ At least seven countries must cooperate to make a telephone message possible.
Perhaps the most extraordinary feature in the Western Electric factories is the multitude of its inspectors. No other sort of manufacturing, not even a Government navy-yard, has so many. Nothing is too small to escape these sleuths of inspection. They test every tiny disc of mica, and throw away nine out of ten. They test every telephone by actual talk, set up every switchboard, and try out every cable. A single transmitter, by the time it is completed, has had to pass three hundred examinations ”

“ Telephone Equipment. Of no less importance than the selective devices is the telephone apparatus. That which is here illustrated is the product of the Western Electric Company, to whom we are indebted for all the illustrations in this chapter.
Dispatcher's Transmitter. The dispatcher, in most cases, uses the chest transmitter similar to that employed by switchboard operators in every-day service. He is connected at all times to the telephone circuit, and for this reason equipment easy for him to wear is essential. In very noisy locations he is equipped with a double head [Page 344] receiver. ”

“ To render the telephone powerful enough to make conversation possible over long distances it was found advisable to substitute for the one telephone a special transmitter, and to insert in the circuit a battery giving a much stronger current than could possibly be excited by the magnet in the telephone at the speaker’s end. ”

“ Giddings.
"Practically the same, dad. The wireless transmitter, like that of the wire telephone, contains a sensitive diaphragm which your voice strikes and sets to vibrating. These vibrations compress and release a capsule of carbon granules which agitate and set in motion an electrical current in two magnets connecting with them. The magnets convey the sound-waves in the form of electrical waves, along wires out to the tip of each wing, where the wires hang down a little way. When a message comes in it is caught by a webbing of antennae wires in our wings." ”

“ The telephone that we generally use has a transmitter which permits but a small portion of the battery power to pass into the wires, owing to the resistance of the carbon diaphragm. The weakness of the current is to a great extent compensated by the exceedingly delicate nature of the receiver. ”

“ Wireless telephony, like wireless telegraphy, but to an even greater extent, is peculiarly suited for the conveyance of marine intelligence. Wireless telephony occupies a unique position in this regard-no operator is required. The additional expense of an operator is an objection to the wireless telegraph in many cases, and forbids its installation. Anybody can operate the wireless telephone. It is also much quicker-words can be spoken more rapidly than they can be put into Morse signals and translated. ”

“ In that way, a single pair of wires can be used for transmitting, simultaneously and without any interference, several different telephone conversations. It takes very much less power than would radio transmission and the conversations are secret. The ordinary telephone conversation can go on at the same time without any interference with those which are being carried by the modulations in high-frequency currents. ”

“ The aerial wire is precisely the same for either wireless telegraphy or wireless telephony. The transmitter of a wireless telegraph set generally uses a spark gap for setting up the electric oscillations, while usually for wireless telephony a vacuum tube is employed for this purpose. The receptor for wireless telegraphy and telephony is the same and may include either a crystal detector or a vacuum tube detector, as will be explained presently. ”

“ The telephone receiver itself serves a useful purpose as an audible signal. An interrupted or alternating current of proper frequency and amount will produce in it a musical tone which can be heard throughout a large room. This fact enables a telephone central office to signal a subscriber who has left his receiver off the switch hook, so that normal conditions may be restored. ”

“ In the case of the wireless telegraph the number of messages which may be sent simultaneously is much restricted. In the case of the wireless telephone, owing to the thousands of separate wave-lengths required for the transmission of speech, the number of telephone conversations which may be carried on at the same time is still further restricted and is so small that all who can employ wires will find it necessary to do so, leaving the ether available for those who have no other means of communication. ”

“ Wireless telegraphy is part of the established order of things. The wireless telephone is practical for limited distance, but is not a commercial rival of the telegraph. Great distances are claimed, but they are matters for proof and speculation.
There is no immediate possibility that wireless telephony will take the place of local exchanges. If the time ever does come that it in any way tends to supplant the line telephone for some uses, it is more than probable that each subscriber must have his own generating station and call up direct. ”

“ We still have our neighbors' call bells, and we could listen to their messages if we were gossips. The telephone service has been extended to great distances—for instance, from Boston to Omaha—not by relays, but by strengthening the blows upon the medium between the transmitting circuit and the receiving one, just as we desire to do in what is called wireless telegraphy, the apparatus of which is almost identical in principle to that employed in telephony. The individual call in telephony is not a success for nearly the same reasons that exist in the case of wireless telegraphy. ”

“ The receiver has an open antenna circuit which is electrically responsive to the transmitted waves and is capable of using those responses to actuate by means of a relay or amplifier any convenient form of signalling apparatus for making audible an electrically transmitted signal, such as a telegraph sounder or a loud speaker. In brief, signals at the transmitter are utilized to control high frequency electrical oscillations which are radiated by an antenna through the ether to the distant receiver and there produce an audible or visible signal. ”

“ To make wireless telephony a success it was necessary to find some way of making perfectly uniform carrier-waves, and then of loading on them waves of speech. Of course, the latter are not sound-waves, because they are not waves of air, but they are electro-magnetic waves corresponding exactly to the sound-waves of air and at the receiving-end they affect the telephone receiver in the191 same way that it is affected by the electric waves which are sent over telephone wires. ”

“ If the electricity with which any conducting body is charged be suddenly disturbed, electrical waves are generated which travel outwards in all directions with the velocity of light. The problem of wireless telegraphy is the problem of producing these waves by means of an instrument called a transmitter, and of recording their impact at a distance by means of an instrument called a receiver. ”