Two were of iron and two of tellurium, it being the gist of Edison's plan to effect the marking of the chemical paper by one metal with a positive current, and by the other metal with a negative current.
"Edison, His Life and Inventions"
Frank Lewis Dyer and Thomas Commerford Martin
Of these receiving pins, one pair-1 and 3-are of iron, and the other pair-2 and 4-of tellurium.
"Edison, His Life and Inventions"
Frank Lewis Dyer and Thomas Commerford Martin
As the perforated tape passes over the transmission drum the advanced rollers 6 or 8 first close the circuit through the perforations, and a positive current passes from the batteries through the drum and down to the ground; thence through the earth at the receiving end up to the other drum and back to the batteries via the tellurium pins 2 or 4 and the line wire.
"Edison, His Life and Inventions"
Frank Lewis Dyer and Thomas Commerford Martin