Seventy-five Years of the Telephone: 

 An Evolution in Technology 



By W. H. MARTIN 



SEVENTY-FIVE years ago— on March 10, 1876— the inventor spoke 

 and his assistant heard the first sentence to be transmitted by tele- 

 phone: ''MR. WATSON, COME HERE; I WANT YOU." Three days 

 earUer, U.S. Patent No. 174,465 had been granted to Alexander Graham 

 Bell for his concept of means for making the conversion between the air 

 vibrations of an uttered sound and their corresponding electrical undulations. 



On this historic occasion, Bell talked into his liquid transmitter, and 

 Thomas A. Watson listened to a tuned-reed receiver. In this receiver, shown 

 at the right of Fig. 1, the free end of a steel armature was caused to vibrate 

 by the undulatory currents through an electromagnet. Bell's famous patent 

 showed such a structure with the free end of the reed attached to the middle 

 of a stretched membrane, as at the left of Fig. 1 . In Bell's liquid transmitter, 

 in the middle of Fig, 1, a wire attached to a sound-vibrated diaphragm varied 

 the length of its contact with some acidulated water, and thus produced a 

 resistance changing in accordance with the impinging sound waves. This 

 sound-controlled variable resistance in a battery circuit provided a means 

 of associating amplification with the conversion of speech waves into their 

 electrical counterparts. Thus, the first telephonic transmission of informa- 

 tion demonstrated the two general principles of making the conversion be- 

 tween sound and electricity which have continued to be embodied uni- 

 versally — after much evolution through invention, research and development 

 — in the transmitters and receivers of commercial telephony. 



Today Bell would be called a scientist. He had been trained for work in 

 the field of speech and hearing. He set himself the problem of transmitting 

 and reproducing speech, which he approached analytically and experi- 

 mentally. Where he thought more knowledge would help him in the solution, 

 he tried to get it. Watson was the engineer of the team; he expressed Bell's 

 ideas in forms for further experimentation and for use. The telephone busi- 

 ness came into being out of such procedures and in a laboratory; that lab- 

 oratory was the progenitor of the Bell Telephone Laboratories. 



In this anniversary article, it has been deemed appropriate to portray 

 the evolution of the methods and technology, and the scope of the activities 

 in Bell Telephone Laboratories and its predecessors in the line of descent, 

 which have been applied to the development of Bell's telephone instruments 

 to bring them to their present state. This portrayal will show that Bell's 



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