An eight-page letter penned in 1878 by Scottish-born inventor Alexander Graham Bell, containing a rare picture of his first telephone system, is up for auction.
The missive, being sold by New Hampshire-based RR Auction, was written by Bell to his father in 1878 after a "lightning accident" threatened the integrity of his fledging invention, the 'Daily Mail' reported.
The letter is highlighted by a one-of-a-kind sketch of two connected telephones, with in-depth instructions to his family on a necessary safety precaution -- one that could possibly save their lives.
Bell writes in the letter, postmarked from Washington DC, on December 30, to his parents that he is "quite troubled by your account of the lightning accident at Tutelo Heights.
The accident shows that the earth terminals of your telephone line are defective for the current found a shorter path to the ground through two of your poles than by the proper path".
And he goes on to draw a remarkable diagram -- two telephones -- showing the correct mechanical assemblage to ensure proper function and, above all, safety.
Bell continues: "As I do not know your connections I shall merely state what connections I should advise in order to prevent a repetition of the accident -- which might have been more serious had the poles not been struck and thus afforded a partial passage to the earth."
Bell was a pioneer in the field of telecommunications and inventor of the "electrical speech machine". He invented the telephone in 1876 with the help of his assistant Thomas A Watson.