What Happens When You Talk into a Telephone Receiver

In Omaha, Nebraska, half-way across the continent and about forty hours from Boston by fast train, a man sits comfortably in his office chair and, with no more exertion than is required to lift a portable receiver off his desk, talks every day to his representative in the chief New England city. The man in Boston hears his chief's voice and can recognise the peculiarities in it just as if he stood in the same room with him. The man in Nebraska, speaking in an ordinary conversational tone, can be heard perfectly well in Boston, 1,400 miles away.

This is the longest talk on record—that is, it is the longest continuous telephone line in steady and constant use, though the human voice has been carried even greater distances with the aid of this wonderful instrument.

The telephone is so common that no one stops to consider the wonder of it, and not one person in a hundred can tell how it works.

At this time, when the telephone is as necessary as pen and ink, it is hard to realise a time when men could not speak to one another from a distance, yet a little more than a quarter of a century ago the genius who invented it first conceived the great idea.

Sometimes an inventor is a prophet: he sees in advance how his idea, perfected and in universal use, will change things, establish new manners and customs, new laws and new methods. Alexander Graham Bell was one of these prophetic inventors—the telephone was his invention, not his discovery. He first got the idea and then sought a way to make it practical. If you put yourself in his place, forget what has been accomplished, and put out of mind how the voice is transmitted from place to place by the slender wire, it would be impossible even then to realise how much in the dark Professor Bell was in 1874.

The human speaking voice is full of changes; unlike the notes from a musical instrument, there is no uniformity in it; the rise and fall of inflection, the varying sound of the vowels and consonants, the combinations of words and syllables—each produces a different vibration and different tone. To devise an instrument that would receive all these varying tones and inflections and change them into some other form of energy so that they could be passed over a wire, and then change them back to their original form, reproducing each sound and every peculiarity of the voice of the speaker in the ear of the hearer, was the task that Professor Bell set for himself. Just as you would sit down to add up a big column of figures, knowing that sooner or later you would get the correct answer, so he set himself to work out this problem in invention. The result of his study and determination is the telephones we use to-day. Many improvements have been invented by other men—Berliner, Edison, Blake, and others—but the idea and the working out of the principle is due to Professor Bell.

Every telephone receiver and transmitter has a mouth-and ear-piece to receive or throw out the sound, a thin round sheet of lacquered metal—called a diaphragm, and an electromagnet; together they reproduce human speech. An electric current from a battery or from the central station flows continuously through the wires wound round the electromagnet in receiving and transmitting instruments, so when you speak into the black mouthpiece of the wall or desk receiver the vibrations strike against the thin sheet-iron diaphragm at the small end of the mouthpiece; the sound waves of the voice make it vibrate to a greater or less degree; the diaphragm is placed so that the core of the electromagnet is close to it, and as it vibrates the iron in it produces undulations (by induction) in the current which is flowing through the wires wound round the soft iron centre of the magnet. The wires of the coil are connected with the lines that go to the receiving telephone, so that this undulating current, coiling round the core of the magnet in the receiver, attracts and repels the iron of the diaphragm in it, and it vibrates just as the transmitter diaphragm did when spoken into; the undulating current is translated by it into words and sentences that have all the peculiarities of the original. And so when speaking into a telephone your voice is converted into undulations or waves in an electric current conveyed with incredible swiftness to the receiving instrument, and these are translated back into the vibrations that produce speech. This is really what takes place when you talk over a toy telephone made by a string stretched between the two tin mouth-pieces held at opposite sides of the room, with the difference that in the telephone the vibrations are carried electrically, while the toy carries them mechanically and not nearly so perfectly.

For once the world realised immediately the importance of a revolutionising invention, and telephone stations soon began to be established in the large cities. Quicker than the telegraph, for there was no need of an operator to translate the message, and more accurate, for if spoken clearly the words could be as clearly understood, the telephone service spread rapidly. Lines stretched farther and farther out from the central stations in the cities as improvements were invented, until the outlying wires of one town reached the outstretched lines of another, and then communication between town and town was established. Then two distant cities talked to each other through an intermediate town, and long-distance telephony was established. To-day special lines are built to carry long-distance messages from one great city to another, and these direct lines are used entirely except when storms break through or the rush of business makes the roundabout route through intermediate cities necessary.

As the nerves reaching from your finger-tips, from your ears, your eyes, and every portion of your body come to a focus in your brain and carry information to it about the things you taste, see, hear, feel, and smell, so the wires of a telephone system come together at the central station. And as it is necessary for your right hand to communicate with your left through your brain, so it is necessary for one telephone subscriber to connect through the central station with another subscriber.

The telephone has become a necessity of modern life, so that if through some means all the systems were destroyed business would be, for a time at least, paralysed. It is the perfection of the devices for connecting one subscriber with another, and for despatching the vast number of messages and calls at “central,” that make modern telephony possible.

To handle the great number of spoken messages that are sent over the telephone wires of a great city it is necessary to divide the territory into districts, which vary in size according to the number of subscribers in them. Where the telephones are thickly installed the districts are smaller than in sections that are more sparsely settled.

Then all the telephone wires of a certain district converge at a central station, and each pair of wires is connected with its own particular switch at the switchboard of the station. That is simple enough; but when you come to consider that every subscriber must be so connected that he can be put into communication with every other subscriber, not only in his own section but also with every subscriber throughout the city, it will be seen that the switchboard at central is as marvellous as it is complicated. Some of the busy stations in New York have to take care of 6,000 or more subscribers and 10,000 telephone instruments, while the city proper is criss-crossed with more than 60,000 lines bearing messages from more than 100,000 “'phones.” Just think of the babel entering the branch centrals that has to be straightened out and each separate series of voice undulations sent on its proper way, to be translated into speech again and poured into the proper ear. It is no wonder, then, that it has been found necessary to establish a school for telephone girls where they can be taught how to untangle the snarl and handle the vast, complicated system. In these schools the operators go through a regular course lasting a month. They listen to lectures and work out the instructions given them at a practice switchboard that is exactly like the service switchboard, except that the wires do not go outside of the building, but connect with the instructor's desk; the instructor calls up the pupils and sends messages in just the same way that the subscribers call “central" in the regular service.

At the terminal station of a great railroad, in the midst of a network of shining rails, stands the switchman's tower. By means of steel levers the man in his tower can throw his different switches and open one track to a train and close another; by means of various signals the switchman can tell if any given line is clear or if his levers do their work properly.

A telephone system may be likened, in a measure, to a complicated railroad line: the trunk wires to subscribers are like the tracks of the railroad, and the central station may be compared to the switch tower, while the central operators are like the switchmen. It is the central girls' business to see that connections are made quickly and correctly, that no lines are tied up unnecessarily, that messages are properly charged to the right persons, that in case of a break in a line the messages are switched round the trouble, and above all that there shall be no delay.

When you take your receiver off the hook a tiny electric bulb glows opposite the brass-lined hole that is marked with your number on the switchboard of your central, and the telephone girl knows that you are ready to send in a call—the flash of the little light is a signal to her that you want to be connected with some other subscriber. Whereupon, she inserts in your connection a brass plug to which a flexible wire is attached, and then opens a little lever which connects her with your circuit. Then she speaks into a kind of inverted horn which projects from a transmitter that hangs round her neck and asks: “Number, please?” You answer with the number, which she hears through the receiver strapped to her head and ear. After repeating the number the “hello” girl proceeds to make the connection. If the number required is in the same section of the city she simply reaches for the hole or connection which corresponds with it, with another brass plug, the twin of the one that is already inserted in your connection, and touches the brass lining with the plug. All the connections to each central station are so arranged and duplicated that they are within the reach of each operator. If the line is already “busy” a slight buzz is heard, not only by “central,” but by the subscriber also if he listens; “central” notifies and then disconnects you. If the line is clear the twin plug is thrust into the opening, and at the same time “central" presses a button, which either rings a bell or causes a drop to fall in the private exchange station of the party you wish to talk to. The moment the new connection is made and the party you wish to talk to takes off the receiver from his hook, a second light glows beside yours, and continues to glow as long as the receiver remains off. The two little lamps are a signal to “central” that the connection is properly made and she can then attend to some other call. When your conversation is finished and your receivers are hung up the little lights go out. That signals “central” again, and she withdraws the plug from both holes and pushes another button, which connects with a meter made like a bicycle cyclometer. This little instrument records your call (a meter is provided for each subscriber) and at the same time lights the two tiny lamps again—a signal to the inspector, if one happens to be watching, that the call is properly recorded. All this takes long to read, but it is done in the twinkling of an eye. “Central's” hands are both free, and by long practice and close attention she is able to make and break connections with marvellous rapidity, it being quite an ordinary thing for an operator in a busy section to make ten connections a minute, while in an emergency this rate is greatly increased.

The call of one subscriber for another number in the same section, as described above—for instance, the call of 4341 Eighteenth Street for 2165 Eighteenth Street—is the easiest connection that “central" has to make.

As it is impossible for each branch exchange to be connected with every individual line in a great city, when a subscriber of one exchange wishes to talk with a subscriber of another, two central operators are required to make the connection. If No. 4341 Eighteenth Street wants to talk to 1748 Cortlandt Street, for instance, the Eighteenth Street central who gets the 4341 call makes a connection with the operator at Cortlandt Street and asks for No. 1748. The Cortlandt Street operator goes through the operation of testing to see if 1748 is busy, and if not she assigns a wire connecting the two exchanges, whereupon in Eighteenth Street one plug is put in 4341 switch hole; the twin plug is put into the switch hole connecting with the wire to Cortlandt Street; at Cortlandt Street the same thing is done with No. 1748 pair of plugs. The lights glow in both exchanges, notifying the operators when the conversation is begun and ended, and the operator of Eighteenth Street “central” makes the record in the same way as she does when both numbers are in her own district.

Besides the calls for numbers within the cities there are the out-of-town calls. In this case central simply makes connection with “Long Distance,” which is a separate company, though allied with the city companies. “Long Distance” makes the connection in much the same way as the branch city exchanges. As the charges for long-distance calls depend on the length of the conversation, so the connection is made by an operator whose business it is to make a record of the length in minutes of the conversation and the place with which the city subscriber is connected. An automatic time stamp accomplishes this without possibility of error.

Sometimes the calls come from a pay station, in which case a record must be kept of the time occupied. This kind of call is indicated by the glow of a red light instead of a white one, and so “central” is warned to keep track, and the supervisors or monitors who constantly pass to and fro can note the kind of calls that come in, and so keep tab on the operators.

Other coloured lights indicate that the chief operator wishes to send out a general order and wishes all operators to listen. Another indicates that there is trouble somewhere on the line which needs the attention of the wire chief and repair department.

The switchboards themselves are made of hard, black rubber, and are honeycombed with innumerable holes, each of which is connected with a subscriber. Below the switchboard is a broad shelf in which are set the miniature lamps and from which project the brass plugs in rows. The flexible cords containing the connecting wires are weighted and hang below, so that when a plug is pulled out of a socket and dropped it slides back automatically to its proper place, ready for use.

Many subscribers nowadays have their own private exchanges and several lines running to central. Perhaps No. 4341 Eighteenth Street, for instance, has 4342 and 4344 as well. This is indicated on the switchboard by a line of red or white drawn under the three switch-holes, so that central, finding one line busy, may be able to make connection with one of the other two, the line underneath showing at a glance which numbers belong to that particular subscriber.

If a subscriber is away temporarily, a plug of one colour is inserted in his socket, or if he is behind in his payments to the company a plug of another colour is put in, and if the service to his house is discontinued still another plug notifies the operator of the fact, and it remains there until that number is assigned to a new subscriber.

The operators sit before the switchboard in high swivel chairs in a long row, with their backs to the centre of the room.

From the rear it looks as if they were weaving some intricate fabric that unravels as fast as it is woven. Their hands move almost faster than the eye can follow, and the patterns made by the criss-crossed cords of the connecting plugs are constantly changing, varying from minute to minute as the colours in a kaleido-scope form new designs with every turn of the handle.

Into the exchange pour all the throbbing messages of a great city. Business propositions, political deals, scientific talks, and words of comfort to the troubled, cross and recross each other over the black switchboard. The wonder is that each message reaches the ear it was meant for, and that all complications, no matter how knotty, are immediately unravelled.

In the cities the telephone is a necessity. Business engagements are made and contracts consummated; brokers keep in touch with their associates on the floors of the exchanges; the patrolmen of the police force keep their chief informed of their movements and the state of the districts under their care; alarms of fire are telephoned to the fire-engine houses, and calls for ambulances bring the swift wagons on their errands of mercy; even wreckers telephone to their divers on the bottom of the bay, and undulating electrical messages travel to the tops of towering sky-scrapers.

In Europe it is possible to hear the latest opera by paying a small fee and putting a receiver to your ear, and so also may lazy people and invalids hear the latest news without getting out of bed.

The farmers of the West and in eastern States, too, have learned to use the barbed wire that fences off their fields as a means of communicating with one another and with distant parts of their own property.

Mr. Pupin has invented an apparatus by which he hopes to greatly extend the distance over which men may talk, and it has even been suggested that Uncle Sam and John Bull may in the future swap stories over a transatlantic telephone line.

The marvels accomplished suggest the possible marvels to come. Automatic exchanges, whereby the central telephone operator is done away with, is one of the things that inventors are now at work on.

The one thing that prevents an unlimited use of the telephone is the expensive wires and the still more expensive work of putting them underground or stringing them overhead. So the capping of the climax of the wonders of the telephone would be wireless telephony, each instrument being so attuned that the undulations would respond only to the corresponding instrument. This is one of the problems that inventors are even now working upon, and it may be that wireless telephones will be in actual operation not many years after this appears in print.