Today, the Three-Cent Silver Trime Coin remembers the first telephone conversation between Boston and Salem, a distance of 14 miles, on February 12, 1877.
From the March 31, 1877 Scientific American magazine:
We have already laid before our readers accounts of the wonderful performances of Professor Bell’s telephone, an instrument remarkable not merely for its phenomenal capabilities but also because of its having been brought to its present state of development within the period which has elapsed since June last.
During that month, Professor Bell exhibited the apparatus at the Centennial, working it over short distances only, and causing it to transmit sound, which reached the opposite terminus very much diminished in intensity.
Without undertaking to follow the inventor through his various improvements, it will suffice here to state that the telephone has recently carried the human voice over a distance of 143 miles (from Boston to North Conway, NH) so that ordinary conversational tones uttered at one end were distinctly audible at the other.
Further even than this, the inventor and his assistant have talked through a wire arranged to give an artificial resistance equal to 40,000 ohms, which is more resistance than the entire length of the Atlantic cable would offer.
There are, however, other obstacles than the resistance, which checks the transmission of the voice over such immense distances.
These the inventor is now endeavoring to overcome; and at the first favorable opportunity, a practical test of the powers of the instrument over one of the transatlantic cables will be attempted.
In the telephone which we illustrated recently in the Scientific American Supplement, a battery current was directly employed.
The most important improvement yet made in the apparatus is the entire abolition of the battery and electro-magnets, and the substitution of the permanent magnet, the electric wave used in transmitting the sounds being generated by the voice itself.
The construction of the instrument will be readily understood from the detailed drawings, Figs. 2 and 4.
A, Fig. 2 is a plate of iron or steel which is fastened to the sounding box, D, Fig. 4.
E is the speaking tube by which sounds are conveyed to or from plate A.
F is a bar of soft iron or magnet; G is a coil of insulated copper wire around the extremity, H, of said bar, and I is an adjusting screw by which the end, H, may be placed as desired in relation to plate, A.
Several of these instruments are placed at different stations upon a line as represented in Fig. 3.
When sounds are made at the mouthpiece of the instrument, the plate, A, is set in motion before the poles of F, which may be a permanent compound magnet and arranged as shown in Fig. 2.
A current of electricity is thus created in the coils, G, surround the poles, and the duration of the current of electricity coincides with the duration of the motion of the plate as it vibrates.
When the human voice causes the diaphragm to vibrate, electrical undulations are induced, in the coils around the magnets, precisely similar to the undulations of the air produced by the voice.
The coils are connected with the line wire, and the undulations induced in them travel through that wire; and passing through the coils of another instrument of similar construction, they are again resolved into air undulations by the diaphragm, A, of the second instrument.
So perfectly is this resolution effected that even a whisper is audible over long distances, and soft tones are even more distinct than loud ones.
It will be evident that it is possible to send by the telephone multiple telegraphic message or multiple verbal communications simultaneously.
In Fig. 3, we have represented a number of telephones connected together, each one, for instance, at a different station, the stations being several hundred miles, perhaps, apart.
To send multiple telegraphic messages, let it be supposed that a certain musical sound is uttered before the telephone No. 1: then telephones Nos. 2, 3, etc., will all repeat that sound.
Now let two musical sounds of different degrees of the gamut be made simultaneously before No. 1.
These also will be repeated by the other instruments, and the same would be true if, before the first instrument, any number of different sounds were made.
Now, let it be previously understood that all messages sent to station No. 2 will be uttered in note C for instance, those to No. 3 in note D, and so on, a different note for each station; then, as the signals for each message differ in pitch from those for all the other messages, the operator has only to fix his attention upon the message sounded in the note he has learned to recognize, and he may ignore all the rest.
In this way, the number of dispatches which may be sent simultaneously is very large.
Where, however, a large number is forwarded, rendering it the more difficult for a receiving operator to recognize his particular note, his message may be automatically received by a resonator provided with a membrane which vibrates only when the note with which the resonator is in unison is emitted by the receiving telephone.
The vibrations of the membrane may be made to operate a circuit breaker, which will operate a Morse sounder or a telegraphic recording apparatus.
Of course where several persons speak in the vicinity of telephone No. 1, their utterances are in a like manner simultaneously transmitted to all the telephones in the circuit.
If this verbal communication should be used for telegraphic purposes, the messages would have to be taken down by the receivers in short hand.
We understand that Professor Bell has patents pending for some further improvements in his apparatus. These we shall notice at some future time.
We are indebted to a correspondent for the sketches whence we have prepared the engravings (Fig. 1, front page) representing Professor Bell lecturing on the telephone, at Salem, Mass., on February 12 last, and also the group in the inventor’s study, in Exeter place, Boston, receiving his communications during the course of the lecture.
The apparatus, an exterior view of which is also given, is all contained in an oblong box about 7 inches high and wide, and 12 inches long.
This is all there is visible of the instrument, which during the lecture is placed on a desk at the front of the stage, with its mouthpiece toward the audience.
Not only was the conversation and singing of the people at the Boston end distinctly audible in the Salem hall, 14 miles away, but Professor Bell’s lecture was plainly heard and applause sent over the wires by the listeners in Boston.
Professor Bell was born in Edinburgh, Scotland, and came to this country about six years ago. His father, Professor A. M. Bell, who became noted as the inventor of a method for teaching deaf mutes to speak, and of a universal system of phonography, is now living in Brantford, Ontario.
Professor Graham Bell, the present inventor, has also been exceptionally successful in the instruction of deaf mutes, and in one case he has enabled a girl who had never produced an articulate sound to pronounce words distinctly after having her under his tuition for the short space of two months.
“If I can make a deaf mute talk,” the now famous inventor is reported to have said, “I can make iron talk.”
We need not add that his promise has been fulfilled.
The Three-Cent Silver Trime Coin shows with the illustrations of the first telephone conversation between Boston and Salem on February 12, 1877.