US1486735A - Apparatus for producing and receiving signals - Google Patents

Description

MaWch-ll 1924. 1,486,735

' R. A. FESSENDEN APPARATUS FOR'PRODUCING AND RECEIVING SIGNALS Filed Aug. 15, 1918 2 Sheets-Sheet l INVENTOR.

BY I ha 61'! ATTORNEYS.

March 11 ,1924. 11,486,735

R. A. FESSENDEN APPARATUS FOR PRODUCING AND RECEIVING SIGNALS Filed Aug:- I5, 1918 2 Sheets-Sheet 2 Hal/R53 44 44 fla /#55 IN VEN TOR.

A TTORNEYS Patented Mar. llll, 11924.

UNITED 'STATES insane earner castes.

' REGINALD A. FESSENDEN, OF BROOKLINE, MASSACHUSETTS[ASSIGNOR T SUBMARINE I SIGNAL COMPANY, OF PORTLAND, MAINE, A CORPORATION OF MIAINE.

APPARATUS FOR PRODUCING AND RECEIVING SIGNALS.

Application filed August 15, 1918.

To all whom it may concern:

Be it known that I, REGINALD A. FnssnN DEN, of Brookline, in the county of Norfolk and State of Massachusetts, a citizen of the United States, have invented new and useful Improvements in Apparatus for Producing and Receiving Signals, of which the following is a specification.

My invention relates to apparatus for producing and detecting signals and other impulses, and for increasing the efliciency of such generation and reception, and more particularly to submarine signaling, and still more particularly to the detection of submarines and similar bodies.

My invention has for its object increased efficiency in the generation and reception of said impulses, and more particularly greater strength and clearness of generation and reception, and the elimination of undesired noises.

My invention will be understood by reference to the drawings in which- Figure 1 is a diagrammatic view of appa- 25 ratus and circuits embodying my invention,

the microphone being in longitudinal section.

Fig. 1 is a plan showing the pointer turned in a different direction from Fig. 1, so and the rheostat circuit.

Fig. 2 is a diagrammatic view in which the microphone is circular.

gig. 3 is a diagrammatic side elevation, an

Fig. 4 a cross section, enlarged, of a ships huiil to which my apparatus is attached, an

Fig. 5 shows in cross section another form of carbon elements arranged to embody my invention.

Heretofore, microphones have been generally constructed of carbon granules or of pairs of carbon balls or plates, and heretofore microphones, consisting of a large number of plates or balls have not been used because they have not been found to give useful results.

Applicant has carried on for a number of years an extendedseries of investigations on this subject, and has found that the reason Why such microphones have not been put in use heretofore, although a priori a large number of contacts in series might be expected to give greater strength, is due to the fact that when a column is built up of Serial No. 249,943.

such plates or .balls, and an impulse is impressed on one end of the column, the density of the column is that of the carbon, butthe elasticity of the column is not that of the carbon, but of the carbon contacts and is of a very much lower order than that of the carbon itself. Y

Consequently, the virtual elasticity of the column being very low, the velocity of an elastic wave along such a column is very slow, and its damping very high. Consequently, if such a column be attached to a diaphragm of a telephone transmitter and a note sounded against the transmitter having a frequency of, say, 200 (two hundred) per second, the elastic wave will travel along the column of contacts at such a slow rate that there may be a large number (say, 7 or 8) complete waves in the column, and consequently the reduction in resistance at the compressional parts of the waves will neutralize the effects of the increased resistance at the expansional part of the waves; and consequently, the change in resistance will be no greater or even less than that due to a single pair of contacts.

Applicant has discovered in the first place that by clamping these disks together under considerable pressure, the virtual elasticity of the contacts may be very greatly increased, so that the elastic wave will have many times the usual length in such columns; for example, 50 (fifty) times the length, and that consequently increased effects can be obtained in this length.

Applicant has also discovered that where the column is not so clamped under pressure, or only under moderate or light pressure, advantage may be taken of the slow propagation of elastic Waves in the column, and the production of nodes in the column, to locate the direction from which the impulses are received.

Applicant has also discovered that such columns are extremely insensitive to disturbing influences, such as the water noises, etc., such as met in submarine signaling and submarine detection.

Applicant has also discovered that such such as oil, or in a non-conducting tube, such as, for example, one formed of rubber, or chrome gelatine.

In Figure 1 is shown one type of apparatus. Here 11, 11 are carbon plates,

either flat, as shown, or somewhat lens' shaped, as shown at 11, 11', or rounded, as shown at 44, 44, Figure 5. These plates are slipped into a rubber, or chrome gelatine, tube, 12, so as to form, with the circular disk metallic terminals, 45, 46, 47, 48, a column of microphonic contacts. This column is held in the rubber tube 12 by the rubber corks 13, 14, though if desired the microphonic column and its terminals may be completely encased in unvulcanized rubber, and the column put under the pressure desired and the rubber vulcanized in place so as to form a homogeneous unit.

For the purpose of maintaining and regulating the proper tension on the column, a support 29 is provided having one end attached to the rubber cork 13 bearing upon one end of the column and the other attached to the rubber cork 14 and bearing upon the opposite end of the column. The support 29 has an air gap at 51 and a coil 52 wound about the support 29 and the air gap, the coil 52 extending over the metal of the support 29 on either side of the air gap. The current through the coil 52 is regulated by a rheostat 54 in series with a battery 53 which supplies the current to the circuit consisting of the battery 53, coil 52, and rheostat 54. When the coil is energized by thecurrent flowing through it, magnetic lines are induced in the metal support which magnetic lines flow across the air gap within the coil and about the exterior of the coil thereby completing a circuit about the coil 52. The ends of the metal forming the poles of the air gap are thus magnetized north and south respec tively, and thus exert a mutual pull upon each other. By means of the support, this pull is exerted upon the ends of the column which is compressed as a whole. It should be noted that the tube 12 will not interfere with the appliance of pressure upon the column since the tube is of rubber and is itself easily compressible. From the contacts 45, 46, 47, 48 conductors 15, 23, 24, 16 are led. to the switch points 20, 21, 22, 230, and a battery 17, and telephone receiver 18 is connected in one of the leads, for example as shown, the lead 15.

On the microphone column being immersed in water and a sound wave of the frequency of 1000 (one thousand) per second being transmitted through the water, since this sound wave will have a length of approximately 4 (four) feet in water, if the microphone column is 8 ft. long, thatis, more than the quarter wave length of the impulse, there will be 2 (two) complete waves acting weaves on the column, and the effect will tend to be diminished if the switch is thrown so that 230 is connected to 22. If the switch 230, however, is thrown to be connected with 20, a variation in the intensity will be observed from what it was when 230 and 22 were connected, and this efiect may be made use of to eliminate undesired noises, as obviously the best position will not be the same for all wave lengths, and by rotating the switch the most sensitive point for. the desired wave length can be determined.

In order to obtain direction, the microphone column as a whole may be rotated, the shaft 31, and pointer 32 being attached to the steel bar 29 and rotatable in the bearing 33. In actual tests it has been found that when the microphonic column is rotated a variation of strength of more than 400 (four hundred) per cent is obtained, according to whether the column is lying side on or pointing towards the source of sound.

.In place of rotating the column to obtain direction, different sections of this microphone lying in different directions or planes may be connected to the receiver. Figure 2 shows such a type, where the rubber tube 25 is circular in shape thus giving uniform compression all around the circle, and four microphone terminals, 26,27,28,290,are brought out to the switch points, 30, 31, 32, 33, and by rotating the switch, 34, 35, the receiver 36 is attached to any pair of contacts desired. In this case, therefore, the microphone column is curved instead of straight and its elements function in the same way as in the form shown in Fig. 1. A suitable location for such microphone rings is shown in Figure 4 at 49, 49', where the microphone rings are placed on the bottom of the boat, either slightly to one side as shown at 49, or directly beneath the keel, as shown at 49.

These methods are therefore valuable also for determining direction of sound. It has also been discovered that the light, rustling noises and other noises made by the rush of water past the ships side can be entirely eliminated by the above construction, and desired noises, such as given off by submarines, and especially low notes due to hull vibrations and propellor noises are brought in with greatstrength, and may be selected, not only from water noises, but also from noises made by boats running on surface.

This type of microphone may be used in any suitable location; for example, in a Water ballast tank, or a specially constructed tank, or in the bilges, or towed overboard, or in oil tanks. A suitable arrangement is shown in Figure 3 and Figure 4, where 40 is the hull of a vessel and 42 the bilge keels, shown in cross section in Figure 4. In this method, applicants distributive elastic wave microphone, or F essenden microphone, may

against machinery noises, though these have little effect in any case.

Where, however, such machinery noises exist, a sound screen as shown in 43, Figure 4;, may be placed around the microphone column with an opening outwards.

While I have herein described the use of this microphone for submarine detection, it is also of general use for submarine detection and for the generation and reception of impulses generally.

'What I claim is 1. Means for submarine signaling comprising. a plurality of plates of microphonic material, arranged as a column, and exposed to the action of the impulses to be received.

2. Means for submarine signaling comprising a plurality of plates of microphonic material, arranged on a dead heat support as a column, and exposed to the action of the impulses to be received.

3. Means for submarine signaling comprising a plurality of plates of microphonic material, arranged as a column, and contained in an elastic tube.

4. Means for submarine signaling comprising a plurality of plates of microphonic material, arranged as a column, and a plurality of electrodes inserted in the column and exposed to the action of the impulses to be received.

5. Means for submarine signaling comprising a plurality of plates of imperfect contact material, arranged as a column and exposed to the action of the impulses to be received, a plurality of electrodes inserted in the column, and a switching means for interconnecting any desired terminals.

6. Means for submarine signaling comprising a plurality of plates of imperfect contact material, arranged as a column in the medium transmitting the impulses, said column being longer than the quarter wave length of the impulse which it is desired to receive.

7. Means for submarine signaling comprising a plurality of plates of microphonic material arranged in a column, each plate forming contact with the face of the adjacent'plate, a plurality of electrodes at intervals in the column forming a plurality of receiving units in series, an elastic tube enclosing said column, caps closing-the ends of said tube and retaining the column under desired pressure, and switch means whereby the number of receiving units in series best adapted for the wave length of the signal to be received may be used.

REGINALD A. FESSENDEN.

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