Journal - Franklin Institute of the State of Pennsylvania (1826)
Franklin Institute, Philadelphia, Franklin Institute (Philadelphia, Pa.) · [Philadelphia : Franklin Institute] · leaf 493
telephones on acommon support so that they could readily be simultaneously appliedto both ears of the person receiving the message. The two telephoneswere mounted on rocking bearings so as readily to adapt themselvesto the ear of the listener. At the same time the handle of the com-mon support, on… … Fig. 6.—Gruys Bi-polar Telephone. Gray invented his bi-polar telephone, shown in Fig. 6, in 1878. Inthis instrument, as the name indicates, there are two magnet poles, eachof which is caused to act on a separate metallic diaphragm, inclined atsuch an angle with respect to each other as to permit…
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