US1850846A

US1850846A - Push rod system for tuning radio circuits

Info

Publication number: US1850846A
Application number: US299854A
Authority: US
Inventors: David A Nicosia; Sippel Harry
Original assignee: Individual
Current assignee: Individual
Priority date: 1928-08-15
Filing date: 1928-08-15
Publication date: 1932-03-22
Anticipated expiration: 1949-03-22

Description

March 22, 1932. D, A NICOSlA ET AL 1,85m846 PUSH ROD SYSTEM FOR TUNING RADIO CIRCUITS Filed Aug. 15, 1928 5 Sheets-Sheet l March 22, 1932. D. A. mcoslA ET AL PUSH ROD SYSTEM FOR TUNING RADIO CIRCUITS Filed Aug. 15, 1928 3 Sheets-Sheet 5 Sheets-Sheet 3 'YYYY D. A. NICOSIA ET AL.

PUSH ROD SYSTEM FOR TUNING RADIO CIRCUITS Filed Aug. 15, 1928 AAA AAA YYY vvvvvvvvv/ March 22, 1932.

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Patented Mar. 22, 1932 DAVID A. NICOSIA AND HARRY SIPPEL, OF CHICAGO, ILLINOIS PUSH ROD SYSTEM FOR TUNING RADIO CIRCUITS AppIication filed August 15, 1928.

Our present invention relates to electrical circuits, and more particularly to a method of and an apparatus for tuning a radio receiving circuit.

Heretofore it has been possible to tune a radio receiving circuit through the means of a plurality of condensers connected together in such a manner as to be contemporaneously operated. This arrangement has to a certain extent proven satisfactory but is highly expensive to manufacture. Also it requires considerable space and results in a somewhat cumbersome receiver. Another disadvantage esides in the fact that it is not possible with this condenser arrangement to attain as fine a tuning as is desired.

An object of our invention, therefore, is to provide an improved and highly simplified radio circuit adapted to be tuned to any wave of which reception is desired and a push rod system for tuning this circuit.

It is also well known in the art that to tune by means of variable inductances instead of condensers results in a simpler construction and a less expensive one. The reason for this is that the ordinary variable condenser if of a good quality is expensive and takes up considerable space. Obviously when the receiving circuit comprises three or more of these condensers it will be appreciated that the size of the radio set will be considerable. On the other hand. inductance coils take up relatively little room and are quite a bit cheaper than variable condensers.

Then. too. it is to be remembered that if the set is of the type wherein the condensers are connected together in multiple so as to be operated contemporaneously, it is not feas' sible to get as fine a tuning and to hold the wave to which the circuit is being tuned as readily as is the case with a set tuned by means of inductances.

lVe propose to provide a radio receiving circuit embodying a plurality of fixed induc- -ances, plurality of fixed condensers asso- 'iatcd with the inductances, and automatic neans for coupling each of the fixed condensers to a variable number of turns of the asso ciated inductance depending upon the length of the wave to which the circuit is being Serial No. 299,854.

tuned; the latter means being common to all inductances so that connections between the inductances and condensers are effected simultaneously.

A further object of the invention has to do with the provision of means arranged to contemporaneously impose additional capacitance in each of the stages of the radio circuit in the event of slight variations in the length of the wave to which the set is being tuned.

A further object of this invention has to do with the provision of means for disconnecting a part of each inductance of the radio circuit from the circuit when it is desired to tune the circuit to receive a lower band of radio waves and yet at the same time permit of the variable number of turns of the remaining part of each inductance in the circuit to A be connected in shunt to an associated fixed condenser.

Still another object of the invention resides in the provision of an improved method of tuning an electrical circuit to given wave H lengths.

Another and further object of our invention is the provision of a method of and an apparatus for tuning a radio circuit with much less work on the part of the operator I than has been feasible heretofore.

Another object is the provision of a tuned radio receiving set including manually operable members for tuning the circuit and an associated chart having data thereon for in dicating to the operator what members must be manipulated in order to tune the set to receive a given radio wave.

A further object of the invention is the provision of an improved circuit for reproducing electrical waves into sound waves including a plurality of loud speakers, one of which is adjusted to reproduce low pitch sounds and the other of which is adjusted to reproduce the higher pitch sounds.

In accordance with the general features of the invention we provide a radio receiving set having a plurality of manually operable rods for coupling a plurality of fixed condensers, one for each stage of the circuit, to a variable number of turns of a plurality of fixed inductances and a chart for indicating which of the rods should be operated in order to tune the set to receive a given wave length.

Other objects and advantages of our invention will more fully appear from the following detailed description taken inconnection with the accompanying drawings illustrating several embodiments thereof and in which:

Figure 1 is a front elevation of a radio receiver embodying the features of our invention;

Figure 2 is a plan view'o-fthe bottom of the receiver and the apparatus thereon with the casing removed therefrom and drawn to an enlarged scale;

Figure 3 is a radio circuit illustrating how thevarious parts of our set are connected together; 7

Figure 4 is a fragmentary vertical sectional view drawn to an enlargedscale and taken transversely through the apparatus shown in Figure 2;

Figure 5 is a fragmentary detail view illustrating. ap'ortion of our novel chart when the chart is pulled outwardly from the front paneli of the radio set Figure 6 is a sectional view taken on substantially the line VIVI of Figure 4: looking. in the direction indicated by the arrows;

Figure 7 is a fragmentary view partly in section taken on substantially the line VIIVII of Figure 4E lookingin the direction indicated by the arrows Figure 8 is a diagrammatic view illustrating the connections of an inductance embody- -ing the features of our invention;

igure 9is a fragmentary sectional view partly in elevation illustrating what we term a trimmer rod for introducing additional capacitance into the radio circuit of our invention when there is a slight variation in the length of the wave to which the set is being. tuned;

Figure 10 is a diagrammatic view illustrating the connections for disconnecting one part of our inductance from the circuit when it isdesired to render the set capable of being used. to tune in on a lower band. of radio waves;

Figure 11 is an elevation of a switch designed to effect the switching. operation illustrated diagrammatically in Figure 1-0, and

Figure 12. is a. modified. form of. detector and. audio circuit designed for use with the circuitshown in Figure 3 and adapted to separately amplify the high and low pitch waves to be reproduced in a plurality of loud speakers connected to the circuit.

It is believed that our novel method of tuning. aradio circuit will be obvious from a de scription of the apparatus by which it may be performed.-

In the drawings:

Likereference characters designate similar parts throughout the several views. The reference character 15 designates generally a radio cabinet disposed on a base 16 carrying the radio apparatus of our invention. The front side of the cabinet is provided with what may be termed a control panel 17 through which extend the ends of a plurality of operating rods 18 adapted to be manipulated by an operator to automatically tune the set as will be fully explained hereinafter. Also extending from the panel 17 is a rheostat control handle or rod 19 and a reset rod 20 for returning all of the rods to their inoperative position when it is desired to render the set inoperative or to put it in a condition wherein it may be retuned to another wave.

Extending from the lower part of the cabinet is a chart designated by the reference character 22 which has its inner end wound up on a roller 23 suitably mounted in the cabinet and being preferably of the shade roller type so as to at all times urge the chart into its innermost position shown in Figure 4. This chart as shown in Figure 5 shows the frequency in terms of kilocyc-les as well as the wave lengths in terms of meters of each station and in addition shows what buttons or rods must be operated in orderto tune the set to receive the w( ve being broadcasted from a given station.

More specifically, the chart comprises six columns. The first column indicates the fre quency of the waves in terms of kilocycles being broadcast-ed from the stations, the second column indicates the radio stations, the third column indicates the wave lengths in terms of meters of each of the stations, the fourth column indicates the top button or red on the panel which must be operated in order to tune the set to receive from anyone of the stations, the fifth column shows the bottom rod or button if any which must be operated to effect tuning of the set to the wave of a given station, and the last or sixth column designatedby the letter T indicates the extent to which a trimmer rod which we shall described more fully hereinafter must be operated in the event of a slight variation in the length of the wave to whichthe set is being tuned so as to effect perfect reception of that wave.

The chart 22 extends through a slot 24 in the front side of the cabinet into the interior of the cabinet and is disposed within a small casing 24 which is positioned on top of the base 16015 the set as shown in Figure l.

By referring to Figure 1 it will be observed 7 these rods with the exception of the one designated by the reference character 18 in F igure 2 comprise what we term tuning rods. The rod 18 which is illustrated in detail in Figure 9 constitutes the trimmer rod previously referred to and which will be more fully explained hereinafter.

The rods extend through a pair of parallel mounting plates of insulation 28 suitably supported upon the base 16 by four parallel rods 29 which are in turn carried by brackets 30 anchored by bolts to the base 16. The number of plates 28 employed is not necessarily limited to two inasmuch as one is provided for each stage of the circuit and obviously a circuit can have considerably more than two stages. The set we have chosen for illustration comprises a two stage set.

Since all of the rods 18 are substantially identical in construction, it is believed that a description of one will suffice for all. Each rod, as previously mentioned, is made of insulation and in addition has mounted thereon one or more metallic sleeves 32 designed to establish an electrical connection between a pair of resilient contacts 33 and 34 bolted to one of the plates 28. Inasmuch as the contacts associated with one plate 28 are the same as those associated with the other plate, it will be evident that a description of one set is suiiicient for both. Each plate has two rows of the contacts 3334, there being one row for the upper row of rods 18 and a lower row for the lower row of rods 18 (Figure 4).

The contacts 33 associated with the upper row of rods 18 are connected or strapped together by means of an electrical conductor 35 which has one of its ends connected to a terminal 36 (Figure 2) of a fixed condenser 37. It is to be noted from Figure 2 that there are two fixed condensers 37, there being one for each plate 28. The two fixed condensers are mounted upon an insulation strip 38 suitably anchored to the two plates 28, the other terminal 39 of each condensers 37 being connected to one end of a conductor 40 which straps together the contacts 33 associated with the lower set of rods 18.

Each of the contacts 34 associated with the upper row of rods 18 is connected by a con ductor 41 to a given number of turns of an inductance 42 (Figures 4 and 8). The number of turns of the inductance 42 connected to each contact 34 may be five, ten or any other predetermined amount.

Each of the contacts 34 associated with the lower row or rods 18 is connected by a conductor 43 to a single turn of the same inductance 42 as shown in Figures 4 and 8. The ends of this inductance 42 are connected by

conductors

44 and 45 to the filament and grid sides, respectively, of a vacuum tube 46 (Figure 3), all of which will be more fully explained hereinafter. An inductance 42' is also associated with the contacts on the other plate 28 as shown in Figure 2. The only difference between the inductance 42 and the inductance 42 resides in the fact that the latter is disposed in a vertical position, whereas the former is disposed in a horizontal position on top of the base 16 of the radio receiving set. The connections between the contacts 34 on the second plate 28 and the coil 42 are the same as those described in connection with the coil 42.

By referring to Figure 4 it will be evident that normally the contacts 32 on the rods 18 are disposed out of engagement with the associated contacts 33 and 34 so that the connection between the contacts is broken. On the other hand, whenever it is desired to tune the set to receive from a given station, certain of these rods are pushed inwardly so as to bring the metallic sleeves 32 on these certain rods into engagement with the associated contacts 33 and 34 whereby the contacts are electrically connected together. For exampl if one of the upper rods 18 was to be pushed inwardly it would result in a set of the contacts 33 and 34 on the left side of the condenser 37 as shown diagrammatically in Figure 8 being connected together thus causing a given number of turns of the inductance 42 to be connected to one side of the fixed condenser 37. Similarly if one of the lower rods 18 is pushed inwardly by the operator to the dotted position shown in Figure 4 it would result in one set of the contacts 33 and 34 on the right side of the fixed condenser 37 as shown in Figure 8 being connectl ed. This means that a certain number of turns of the inductance 42 will be connected to the right side of the fixed condenser 37. As will become more apparent with the progress of the present description, by varying the total number of turns of the inductance 42 connected to the fixed condenser 37 it is possible to vary the effect of the condenser on the inductance and in that way vary the reactancc of the associated circuit. lVhat has been said i in connection with the inductance 42 is equaL ly well applicable to the inductance 42 which is identical in construction to the inductance 42 and has identically the same connections with the other fixed condenser 37.

The trimmer rod 18 carries one or more metallic sleeves 32 which are each designed to constitute part of a variable condenser 48 (FiguresS and 9). This sleeve 32 is at all times engaged by a contact 33 which is connected to the strap wire 40. Also associated with the sleeve 32 and disposed in axial alignment therewith is a metallic sleeve 34 secured to the panel or plate 28 and which takes the place of a contact 34. This tube 34 is designated diagrammatically in Figure 8 and is connected to the strap wire 35 previ ously described. From Figure 9 it will be evident that by moving the rod inwardly it is possible to cause the sleeve 32' to telescope "the sleeve 34 and in that way introduce additional capacitance in the circuit associated with the inductance 42 and the associated fixed condenser 37. In other words, the sleeve 32' and the tube 34 when connected together comprise a variable condenser which is designated by the reference character 48 in the diagrammatic view shown in Figure 8. It will be noted from Figure 9 that each of the plates carries a tube 34 and that for this reason a variable condenser 48 is associated with each of these plates 28. 7

The outer or button end of the rod 18 (Figure 9) is provided with markings 50 which are suitably graduated in terms of digits indicating the values contained in the tuning column of the chart 22. Now if the station being tuned in is one which requires the use of this tuning or trimmer rod to get clear reception as where there is a slight variation in the length of the wave being broadcasted, the tuning rod is pushed inwardly until the digit of the marking 50 is reached. For example. if KYlV is the station from which reception is desired, the tuning rod is moved inwardly until the digit 2 (Figure 5) is adjacent the panel 17 In other words, the tuner permits of finer tun ing and enables one to tune in a station on the receiver even though the stations program is being broadcasted on a slightly different wave length.

We shall now describe the mechanism for resetting or returning the rods to their inoperative position when it is desired to render the set inoperative or else to tune it to another station. This mechanism is clearly shown in Figures 4 and 7 and comprises a pivotally mounted member 52 having an enlarged upper arm 53 provided with a plurality of vertical slots 54for receiving the

rods

18 and 18. Each of these rods is provided with a collar 55 secured to it adjacent the front of the cabinet as shown in Figure 4. When the arm 53 is in the full line position shown in Figure 4 it abuts the collars 55 on the

rods

18 and 18. The intermediate portion of the member 52- is provided with ears 56 pivotally mounted upon a pin 57 carried by a lug 58 secured to the front of the cabinet as shown in Figure 4. The lower arm of'the lever-like member 52 is fastened to one end of the reset or operating rod 20 extending through an opening 59 in the front of the cabinet. Positioned between the front wall of the cabinet and the lower arm 60 of the member 52' is a weak spring 61 which is only of sufficient strength to prevent undue movement of the rods 18 when the member 52 is in the full line position shown in Figure 4. On the other hand, when this member is moved to either one of the two dotted positions shown in Figure 4 the friction between the member and the rods is sufiicient to overcome the resiliency of the spring. This means that if the reset rod '20 is operated to move the member 52 into one of the dotted positions shown in Figure 4, it will remain in that position until it is moved back into the full line' position. Movement of this member from the dotted position to the full line position in Figure 4 will result in it engaging the collars 55 on any of the rods which have been operated so as to cause them to be returned to their inoperative positions.

Vie shallnow proceed to describe briefly the circuit associated with the

inductance

42 and 42 of our receiving set shown in Figure 3. Associated with each of the

inductances

42 and 42" is a primary winding or inductance 65. The winding 65 associated with inductance 42 has its ends connected to ground and antenna wires 66 and 67. The winding 65 associated with inductance 42 has its ends connected to

wires

68 and 69 leading to the B battery 70 and the plate of tube 46 respectively. The lead wire 68 is also connected by means of a conductor 71 to the filament of a second three element vacuum tube 72 associated with inductance 42. Positioned in this wire lead 71 is a fixed condenser 73.

The three element tube 46 has its grid connected to the antenna lead 67 by means of a conductor 74 including a variable condenser 75 and a resistor 7 6. The plate of this tube as previously described is connected to a primary winding 65 associated with inductance 42. The filament is connected to leads 77 and 78 which are in turn connected to the leads 7 9 and 80 respectively of the filament of the other tube 72. The wire lead 77 is connected by a conductor 81 through the variable resistance or volume control 82 operable by handle 19 to the negative side of an A battery 83 having its other side connected to lead 80 of the filament of tube 7 2. This A battery serves to supply current to the filaments of the tubes. Lead 80 is also connected to the negative side of the B battery by means of a conductor 84. The positive side of the B battery as previously described is connected to conductor 68 associated with the primary winding 65 of the second inductance 42.

It will be noted from Figure 3 that the conductor 44 serves to connect corresponding ends of the two

inductances

42 and 42. The other end of the inductance 42 is connected by means of a conductor 85 through a fixed condenser 86 to the grid of the tube 7 2. This conductor 85 is also connected to the lead 80 of the filament of this tube through a resistor 87 and a conductor 88. The plate of tube 72 is connected to a conductor 89 having connection with one end of a wire lead 90 including a condenser 91, which lead has its other end secured to the filament supply wire 79. The tube 7 2 comprises the detector tube of the receiver and discharges into an audio reproducing circuit designated generally by the reference character 92.. The reference characters 94 designate diagrammatically the rods 18 in Figure 3 including the sleeves thereon for establishing connections between the contacts of the inductances.

The circuit 92 comprises a transformer 96 having one end of its primary winding 97 connected to the conductor 89 of the plate tube 72 and has its other end connected to the positive side of the B battery. The secondary winding 98 of this transformer has one of its ends connected to the grids of two three-

element vacuum tubes

100 and 101. It will be noted that the grids of these tubes are connected in series by the conductor 99. The other side of the winding 98 is connected through a 0 battery 102 to a wire lead 103 having connected to it the negative sides of the two filaments of the

tubes

100 and 101. The positive sides of the filaments are connected in series by a conductor 10% which has a connection with the positive side of the A battery.

The conductor 103 has a connection with the minus side of the same battery as indicated at 105. It will be thus evident that the two filaments of these tubes are also connected in series. The plate of tube 100 is connected by a conductor 106 to one side of a loud speaker jack 107 and the plate of tube 101 is connected by a conductor 108 to one side of a loud speaker jack 109. The other side of jack 107 is connected by a conductor 110 to the positive side of a B battery and the other side of the jack 109 is connected by a lead 111 to the positive side of another B battery. One of these jacks is designed to be connected to a loud speaker for reproducing low pitch sounds and the other is designed to be connected to a loud speaker for reproducing high pitch sounds. It will, of course, be evident that it is desirable to employ a higher voltage B battery for the low pitch speaker than is required for the high pitch speaker.

The operation of our novel radio receiving set as illustrated diagrammatically in Figure 3 is briefly as follows: Initially and just prior to the tuning of our radio receiving set all of the rods 18 including the trimmer rod 18 are disposed in the full line positions shown in Figure 4. These rods are moved to their inactive positions by the reset plunger rod 20 previously described. Obviously when all of the rods 18 are out of engagement with the corresponding

contacts

33 and 3 1 it means that the condensers 37-37 associated with the

inductances

42 and 42 are disconnected from the inductances.

Now upon the operator ascertaining the station from which reception is desired, the chart 22 is pulled outwardly from the cabinet until the station desired is found thereon. Assuming the station to be tuned in is WDAP (Figure 5) the operator will observe that the top button rod 60 must be operated as well as the bottom or lower button rod 9. Thereafter all the operator has to do in order to tune this station in the set is to pull the two

button rods

60 and 9 outwardly. This results in each condenser 37 being connected to a given number of turns of the associated inductance coil l2-42. It is to be noted that these rods are designed to contemporaneously tune all stages of the circuit whether it be a two three or more stage circuit. That is to say, although we have only illustrated a two stage circuit the invention is not to be thus limited for obviously the same rods 18 can be used to tune additional stages by merely associating with the rods additional contacts and inductances.

Referring to Figure 3 it will be evident that the incoming wave is amplified by the radio frequency tube 46 and the resultant wave is acted upon by the inductance 42 and delivered to the detector tube 72. From the detector tube the audio frequency wave is delivered to the audio or reproducing circuit 96 which is connected to loud speakers through the

jacks

107 and 109. Each of the two

audio tubes

100 and 101 receives audio frequency impulses from the transformer 96 and deliver these impulses in an amplified condition to the associated low pitch and high pitch loud speakers. This loud speaker arrangement insures a better reproduction of all notes of the sound waves being transmitted.

Should it be found that there is a slight variation in the length of the wave of the station being tuned in on our set this varia tion can be compensated for by the trimmer rod 18. The operator then refers to the chart again and finds from the last column of this chart that the trimmer rod should be pushed inwardly three notches. Of course, it will be evident from our previous description of this trimmer rod shown in Figure 9 that inward movement of the rod results in the movement of the sleeves 32 within the tubes 34 and thereby adds additional capacitance to the connections associated with the condensers 37 (Figure 8). This means that the reactance of the circuit is changed to accommodate the slight variation in the length of the wave being tuned in on a set.

When it is desired to render the set inoperative or to tune it in on another station, the reset rod 20 is moved from one of the dotted positions in Figure 4: to the full line position thus returning all rods to their normal or inactive positions.

In some instances it may be desirable to have a radio set adapted to receive the lower Wavelengths. It will be evident that in order to render the ordinary set capable of receiving a band of lower radio waves the inductances of the set must be considerably decreased. We have in Figures 10 and 11 illustrated a simple switch construction for automatically disconnecting a part of each inductance coil from the circuit without in any way interfering with the connecting of the turns of the remaining part of the inductance in the circuit with the associated fixed condensers.

Referring to Figure 10 it will be noted that the inductance 142 differs from the inductance 42 shown in Figure 8 in that it is divided into two parts and has its adjacent ends 143 and 144 connected to adjacent contacts of a switch 145. Outside of this difference the coil 142 and the associated contacts as well as the connections associated with the condenser 187 are identical in every respect to the inductance constructions shown diagrammatically in Figure 8. lvioreover, this inductance coil 142 is connected to the radio circuit in practically the same way as the inductances '42 and 42. The filament lead wire 44 associated with the inductance 142 is is connected to a movable switch arm 146 of the switch 145. This switch arm 146 is made of metal preferably copper-and has its free end adapted to engage a contact 147 secured to a wire 148 leading to an end of the inductance coil 142. r

The switch arm 146 also has fastened to it and movable therewith a bakelite arm 149 which carries a metal contact strip designed to connect the contacts of the two leads 143 and'144. The switch arm, its associated parts and the contacts are all mounted upon a bakelite base 152.

It will be evident that there must be one of these switches for each of the inductances 142. The switch arms 146 of each of these switches are connected together by a com-- mon operating shaft 153 whereby both switches may be operated contemporaneous- 1y, This shaft may have a handle disposed in the rear of the set or if desired the handle may Sextend from the front panel 17 (Figure 1' i r The operation of this switch construction is briefly as follows: When the switch arm 146 is in the full line position shown in Figures 10 and 11 the entire inductance associated therewith will be disposed in the circuit due to the fact that the filament lead 42 is connected through the arm 146 and the lead Obviously this movement of the arm results i in the contact blade being moved out of engagementwith the two leads 143 and 144 into the dotted position shown in Figure 11. The current will then flow from the lead 44' directly into the lead: 144 and thereafter through the remaining part of the inductance to the grid lead 45'. a

VVhen the inductance is in this condition it is only possible to tune with the lower set of button rods 18 since the part of the inductance associated with the contacts of the upper set of button rods has been disconnected from the circuit. This bottom set of tuning rods as well as the trimmer rod 18 may be used to tune in the lower Wave lengths.

In Figure 12 we have illustrated a modified form of audio frequency or reproducing circuit for use in connection with the circuit shown in Figure 3 in place of the circuit of the detector tube 7 2 and the audio frequency circuit 96. In this modified form of circuit the lead 85including the fixed condenser 86 is connected to the grids of two detector tubes -160. Each of these tubes receives part of the wave being'amplified and transmits these separate parts or waves to separate sets of audio frequency amplifier tubes 161162 and 163164. That is to say, the output of each of the tubes 160 is amplified separately and independently from the output of the other tube 160. Inasmuch as thebattery connections for these tubes are more or less conventional and are believed to be obvious from the diagrammatic illustration in Figure 12, it has not been thought necessary to describe these connections in detail. 7 V

The impulses leaving detector tube 160 are amplified by the two

audio tubes

161 and 162 and are delivered to a loud speaker jack adapted to be connected to a loud speaker. Similarly the output of the other or lower detector tube 160 (Figure 12) is amplified by the two' audio tubes 163 and 164 and is thereafter delivered to the loud speaker ack One of the loud speakers connected to th jacks 165-166 is adjusted so as to more reads ily reproduce the higher pitch sound waves and the other is adjusted so as to more readily reproduce the lower pitch sound waves. These two loud speakers connected to the jacks 165 and 166 operate contemporaneously and give a much better reproduction of the sound wave broadcasted than is possible with aloud speaker which has a socalled medium ad ustment. Infact, with thisarrangement we find that we can obtain a much better reproduction of music without any distortion of the low pitch or high pitch notes.

' We desire it understood that although if we have illustrated and described in detail the preferred embodiments of our invention, the invention is not to be thus limitedbut only insofar as defined by the scope and spirit of the appended claims.

We claim asour invention 1. In a radio circuit, an inductance for each stage of the circuit,a condenser associated witheach of said inductances, and mechani cal means for selectively coupling said'con densers to a variable number of turns of said inductances so as to tune the circuit to given waves, said mechanical means comprising a plurality of manually operable rods, each rod being associated with a given turn of each of the inductances so that by a manipulation of said rods a variable number of turns is coupled to the condenser.

2. In a radio circuit including a plurality of stages, an inductance for each stage, a condenser associated with each of said inductances, mechanical means for selectively coupling said condensers to a variable number of turns of said inductances to tune the circuit, said mechanical means comprising a plurality of manually operable rods, each rod being associated with a given turn of each of the inductances so that by a manipulation of said rods a variable number of turns is coupled to the condenser, and manually operable means arranged to simultaneously move a plurality of said rods to their initial position.

3. In a radio circuit including a plurality of stages, an inductance for each stage, a condenser associated with each of said inductances, mechanical means for selectively coupling said condensers to a Variable number of turns of said inductances comprising a plurality of manually operable rods each of which is associated with a given turn of each or the inductances, other manually operable rods each of which is associated with a plurality of turns of each of the inductances, and switch means arranged operable simultaneously to render movement of said latter rods ineffective to tune the circuit.

4. In a radio circuit including a plurality of stages, an inductance for each stage, a condenser associated with each of said inductances, mechanical means for selectively coupling said condensers to a variable number of turns of said inductances to tune the stages, said means comprising a plurality of manually operable rods each of which is associated with a given turn of each of the inductances, other manually operable rods each of which is associated with a plurality of turns of each of the inductances, switch means arranged operable simultaneously to render movement of said latter rods inellective to tune the circuit, and means adapted to engage a plurality of rods to simultaneously move them in one direction.

In testimony whereof, we have hereunto subscribed our names at Chicago, Cook County, Illinois.

DAVID A. NICOSIA. HARRY SIPPEL.