On this day 140 years ago, the 29 year-old Scot Alexander Graham Bell (1847-1922) and his assistant Thomas A. Watson (1854-1934) had, through experiments conducted since 1875, improved the technique of sound transmission via a wire to a point that what was said at one end of the wire could be understood at the other end.
Here is what he wrote in his lab notebook on March 10, 1876:
1.The improved instrument shown in Fig.I was constructed this morning and tried this evening. P is a brass pipe and W the platinum wire M the mouth piece and S the armature of the Receiving Instrument. Mr Watson was stationed in one room with the Receiving Instrument. He pressed one ear closely against S and closed his other ear with his hand. The Transmitting Instrument was placed in another room and the door of both rooms were closed. I then shouted into M the following sentence: “Mr. Watson – come here – I want to see you”. To my delight he came and declared that he had heard and understood what I said. I asked him to repeat the words. He answered “You said ‘Mr. Watson – come here – I want to see you’.” We then changed places and I listened at S while Mr. Watson read a few passages from a book into the mouth piece M. It was certainly the case that articulate sounds proceeded from S. The effect was loud but indistinct and muffled. If I had read beforehand the passage given by Mr. Watson I should have recognized every word. As it was I could not make out the sense – but an occasional word here and there was quite distinct. I made out “to” and “out” and “further”, and finally the sentence “Mr. Bell do you understand what I say? DO – YOU – un- der - stand – what – I – say” came quite clearly and intelligibly. No sound was audible when the armature S was removed.