Kellogg Transmitter

The transmitter of the Kellogg Switchboard and Supply Company, originally developed by Mr. W.W. Dean and modified by his succe ors in the Kellogg Company, is shown in Fig. 43. In this, the electrode chamber, instead of being mounted in a stationary and rigid position, as in the case of the White instrument, is mounted on, and, in fact, forms a part of the diaphragm. The electrode which is a ociated with the mica washer instead of moving with the diaphragm, as in the White instrument, is rigidly connected to a bridge so as to be as free as po ible from all vibrations. Referring to Fig. 43, which is a horizontal cro -section of the instrument, 1 indicates the diaphragm. This is of aluminum and it has in its center a forwardly deflected portion forming a chamber for the electrodes. The front electrode 2 of carbon is backed by a disk of bra and rigidly secured in the front of this chamber, as clearly indicated. The rear electrode 3 , also of carbon, is backed by a disk of bra , and is clamped against the central portion of a mica disk by means of the enlarged head of stud 6 . A nut 7 , engaging the end of a screw-threaded shank from the back of the rear electrode, serves to bind these two parts together securely, clamping the mica washer between them. The outer edge of the mica washer is clamped to the main diaphragm 1 by an aluminum ring and rivets, as clearly indicated. It is seen, therefore, that the diaphragm itself contains the electrode chamber as an integral part thereof. The entire structure of the diaphragm, the front and back electrodes, and the granular carbon within are permanently a embled in the factory and cannot be di ociated without destroying some of the parts. The rear electrode is held rigidly in place by the bridge 5 and the stud 6 , this stud pa ing through a block 9 mounted on the bridge but insulated from it. The stud 6 is clamped in the block 9 by means of the set screw 8 , so as to hold the rear electrode in proper position after this position has been determined. IMG:384091999325875926_fig043_t.gif.png:Illustration_ Fig. 43. Kellogg Transmitter Fig. 43. Kellogg Transmitter View full size illustration. In this transmitter, as in the transmitter shown in Fig. 42, all of the working parts are insulated from the exposed metal casing. The diaphragm is insulated from the front of the instrument by means of a washer 4 of impregnated cloth, as indicated. The rear electrode is insulated from the other portions of the instrument by means of the mica washer and by means of the insulation between the block 9 and the bridge 5 . The terminal for the rear electrode is mounted on the block 9 , while the terminal for the front electrode, shown at 10 , is mounted on, but insulated from, the bridge. This terminal 10 is connected with the diaphragm and therefore with the front electrode by means of a thin, flexible metallic connection. This transmitter is provided with damping springs similar to those of the White instrument. It is claimed by advocates of this type of instrument that, in addition to the ordinary action due to the compre ion and decompre ion of the granular carbon between the electrodes, there exists another action due to the agitation of the granules as the chamber is caused to vibrate by the sound waves. In other words, in addition to the ordinary action, which may be termed the piston action between the electrodes , it is claimed that the general shaking-up effect of the granules when the chamber vibrates produces an added effect. Certain it is, however, that transmitters of this general type are very efficient and have proven their capability of giving satisfactory service through long periods of time. Another interesting feature of this instrument as it is now manufactured is the use of a transmitter front that is struck up from sheet metal rather than the employment of a casting as has ordinarily been the practice. The formation of the supporting lug for the transmitter from the sheet metal which forms the rear casing or shell of the instrument is also an interesting feature.