. The Bell System technical journal . Fig. 1—Sketch, illustrating Bells conception of the telephone, used in his first patent application of 1876. paper,1 I should like to refer briefly to a few of the stages in the evo-lution of the present day instrument. You will recall that Bellsoriginal telephone (Fig. 1) was electromagnetic in principle and acted Ior a more complete account see paper by H. A. Frederick, The Developmentof the Microi)hone, Bell Telephone Quarterly, July, 1931. THE CARBON MICROPHONE 165 both as a transmitter and as a receiver. It was, however, veryInefficient and Bell himse
. The Bell System technical journal . Fig. 1—Sketch, illustrating Bells conception of the telephone, used in his first patent application of 1876. paper,1 I should like to refer briefly to a few of the stages in the evo-lution of the present day instrument. You will recall that Bellsoriginal telephone (Fig. 1) was electromagnetic in principle and acted Ior a more complete account see paper by H. A. Frederick, The Developmentof the Microi)hone, Bell Telephone Quarterly, July, 1931. THE CARBON MICROPHONE 165 both as a transmitter and as a receiver. It was, however, veryInefficient and Bell himself suggested that some other principle suchas that of variation of electrical resistance might overcome thedifficulty. He therefore devised the liquid transmitter In which asmall platinum wire (Fig. 2), attached to a drumhead of gold-beaters. Fig. 2—Bells liquid transmitter. skin, is dipped into a small quantity of acidulated water in a con-ducting cup. The extent of the area of contact between the liquidand the wire is altered by the motion of the latter, thus altering theresistance in a continuous manner. It was with this instrument thatthe first complete sentence, Mr. Watson come here—I want you,was successfully transmitted on March 10, 1876. This achievement 166 BELL SYSTEM TECHNICAL JOURNAL stimulated others to work on the problem of a variable resistanceelement and many new devices appeared in the next few years, themost sensitive of which utilized a single loose contact, carbon in oneform or another being used as the contact material.
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