NEW MICRO-TELEPHONIC APPARATUS.
Despite the simplicity of their parts, and the slight value of the materials employed, the existing micro-telephonic apparatus keep at relatively high prices, and the use of them is often rejected, to the benefit of speaking tubes, when the distance between stations is not too great. We propose to describe a new style of apparatus that are in no wise inferior to those in general use, and the price of which is relatively low.
The microphone transmitter may have several forms. The most elementary of these consists of two pieces of carbon, from one to one and a quarter inches in length by one-half inch in width, between which are fixed two nails, about two inches in length, whose extremities, filed to a point, enter small conical apertures in the carbons. Fig. 1 gives an idea of the arrangement.
Fig. 1.
Fig. 2 represents a model which is a little more complicated, but which gives remarkable results. The largest nail is here two inches in length, and the shortest three-quarter inch.
Fig. 2.
The receivers may be Bell telephones of the simplest form found in the market (Fig. 3); but for these there may be substituted a bar of soft iron, cast iron, or steel, one of the extremities of which is provided with a bobbin upon, which is wound insulated copper wire 0.02 inch in diameter. The apparatus is mounted like an ordinary Bell telephone. A horseshoe electro may also be used, and the poles be made to act (Fig. 4). The current sent by the transmitter suffices to produce a magnetic field in which the variations in intensity produced by the microphone succeed perfectly in reproducing speech and music. With four Leclanche elements, the sounds are perceived very clearly. The elements used may be bichromate of potash ones, those of Lelande and Chaperon, etc.