US2326738A - Radio receiver - Google Patents

Description

Aug. 17, 1943. E. F. ANDREWS RADIO RECEIVER 8 Sheets-Sheet 1 Original Filed May 24, 1939 4 wwfl Maw,

1943. E. ANDREWS 2,326,738

v RADIO RECEIVER Original Filed May 24, 1 939 8 Sheets-Sheet 3 ll/Il 1943. E. F. ANDREWS 2,326,738

RADIO RECEIVER Original Filed May 24, 1939 8 Sheets-Sheet 4 Jill j w m az WA-IIIIHI Aug. 17, 1943. E. F; ANDREWS RADIO RECEIVER Original Filed May 24, 19:9

8 Sheets-Sheet 5 Aug. 17, 1943. EQ F ANDREWS 2,326,733

RADIO RECEIVER Original Filed May 24, 1939 8 Sheets-Sheet 6 gwwdfdrzdzwa Aug. 17, 1943. F, ANI'DREWS' 2,326,738

RADIO RECEIVER Original Filed May 24, 1939 8 Sheets-Sheet 7' gJwMfdmea/Z 1943- E. F. ANDREWS 2,326,738.

RADIO RECEIVER Original Filed May 24, 1939 8 Sheets-Sheet 8 Patented Aug. 17, 1943 I imrro I, FTN'E reigns (iriginal application May 24, 1939, Serial No. 275,437. Divided and this application July 19,

1941, Serial N0. 403,094

18 Claims.

This invention relates to radio receivers and particularly to radio receivers embodying tuning devices of the stop-on-carrier type, and this application is a division of my application Serial No. 275,437, filed May 24, 1939, on Radio receivers. Such devices have been described and claimed in Patent No. 1,700,281 and Patent-No. 1,700,282, issued January 29, 1929, to Elmer Burns and Theodore Cohen, and in my co-pend ing application Serial No. 219,713, filed July 18-, 1938 (now Patent No. 2,262,218, granted November 11, 1941). In receivers of this type, tuning is effected by power means adapted to be set in operation by manually actuated means and adapted automatically to effect the quick stoppage of the tuning means when the receiver has been tuned to the carrier Wave of a broadcasting station received with sufiicient strength. The manually actuated means suitably comprises means controlling the change of an electric current or voltage, and may be located at a point remote from the receiver, from which point control may be effected by means of a simple cable, or by other communicating means.

One of the objects of the present invention is to provide an improved radio receiver of this type.

A further object of the invention is to provide means whereby the effect of static and other undesired electrical disturbances are minimized or prevented, thus avoiding automatic stoppage where there is no desired signal.

A further object of the invention is to provide an improved mechanism whereby the tuning device may be arrested more precisely at positions of more exact resonance.

A further object is to provide a receiver of this type in which the sensitivity of the automatic tuning means may be readily controlled (from a remote point, if desired), whereby the set can be adapted for tuning in a relatively small number of the strongest stations or a greater number of stations, including distant stations, the signals from which are comparatively weak.

A further object of the invention is to provide an improved arrangement whereby vacuum tube means operate gas tube means connected to magnetic means for quickly stopping the tuning de- V108.

A further object is the provision of condenser storage means cooperating with the gas tube to produce faster stoppage of the tuning means.

A further object of the invention is to produce an improved type of stop-on-carrier stopping relay.

A further object of the invention is to provide improved means for securing the greatest automatic control of the set with small number of simple controls.

A further object of the invention is to provide simple and eiiective means for ole-ionizing a gas triode employed for these purposes. I

A further object of the invention is to provide an improved automobile radio set and an improved installation thereof in an automobile.

A further object of the invention is to provide an improved means of increasing the sharpness of the circuit controlling automatic stoppage.

Other objects, advantages and capabilities of the invention will appear from the following description of preferred embodiments thereof, taken in conjuncion with the accompanying drawings in which:

Fig. 1 is a wiring diagram of a radio receiver embodying the invention and intended primarily for alternating current operation in the home;

Fig. 2 is a similar diagram of a radio receiver embodying my invention and intended primarily for operation in an automobile from the automobile storage batter c Fig. 3 is a fragmentary sectional plan View showing the arrangement of certain mechanism or" the radio receiver shownin Fig. 1;

Fig. i is a fragmentary sectional detail, the section being taken on the line i i of Fig. 3;

Fig. 5 is a fragmentary section on a larger scale, the section being taken on the line 5-5 of Fig. 3;

Fig. 6 is an elevational detail showing'a modifled form of operating means for. the reversing switch;

Fig; 7 cator dial which may be employed in radio receiving sets embodying my invention;

Fig. 8 is a fragmentary sectional detail view therethrough, the section being taken on the line 3-3 of Fig. 7;

Fig. 9 is a perspective view of a station indicatis a front elevational View of an indithe section being taken on the line I3--i.-3 of Fig. 17. and illustrating the construction of the stop-omcarrier clutch-brake relay embodied in the receiver;

Fig. 14 is a fr gmentary elevational View of another form of stop-on-carrier clutch-brake relay which may advantageously be employed in either of the embodiments of the invention;

15 is a fragmentary sectional elevation therethrough on a larger scale, the section being taken on the line l-I5 of Fig. 14;

Fig. 16 is a section detail taken on the line l-lfi of Fig. 15;

Fig. 17 is a wiring diagram of an automatic control system embodying my invention, similar to that of Fig. 1;

Fig. 18 is a fragmentary front elevation showing part of the tuning and volume control mechanism mounted on a chassis;

Fig. 19 is a side elevation and partial cross sectional view of Fig. 18;

Fig. 20 is a fragmentary wiring diagram showing certain modifications which may be made in the wiring diagram of Fig. 1; and

Fig. 21 is a similar fragmentary wiring diagram showing further modifications which may be incorporated in this wiring diagram.

Referring to the drawings and particularly to Fig. 1, the radio set illustrated therein is a super- -eterodyne set comprising an antenna circuit 23,

a radio frequency tube iii, an oscillator and demodulator tube 22, intermediate frequency tubes 23 and 24, a diode detector and first audio tube 25, and a power tube 28 which is connected to a loud speaker (not shown) in known manner. Tube 23 may suitably be a 6K7 tube, the tube 22, a 6A8 tube, tubes 23 and 2%, 6K? tubes, and tubes 25 and 25 a GQZG and GLSG tube, respectively. The tubes 2!, 22, 23, 24 and 25 are coupled together in cascade by transformers 2?, 28, 28, and 3B. The output of the tube 25 is resistance coupled through a condenser 3| to the'grid of the power tube 2%. Theset is tuned by condensers 32, 33 and 3a, which are connected together in a, gang, as indicated by the dotted lines 35. These condensers are adapted to be tuned by a reversible motor 36.

The transformer 3i! comprises a Winding 31 which is loosely coupled to the primary of the transformer. This winding is sharply tuned by the condenser 03 and has one end connected to the grid of the stop-on-carricr triode 39. The other end of the winding 3? is connected to one end of the secondary of the transformer which is connected through resistor 4!, resistor 42, and resistor M3 to ground and to the cathode of the rectifier elements of the tube 25. The connected ends of the winding 3? and of the secondary of the transformer 38 are by-passed through condenser 49. The other end of the secondary of the transformer 30 is connected to the diode plates of the tube 25. The triode 3-9 may be so biased as to draw plate current at all times and to produce a sharp rise in its plate current, as the alternating current signal in the coil 3! impressed on its grid substantially exceeds the negative bias, also impressed on its grid, from the diode plate of the tube This sharp rise in plate current produces a voltage across a resistance in the cathode circuit which constitutes the stop-on-carrier signal. The resistances 12 and 43 are paralleled by a condenser 44 and the winding 55 of a potentiometer which, together with the slider 43, constitutes the volume con trol of the set. The slider 46 is connected ow, primaries of transformers 5b and A secondary 5! of the transformer 56 supplies current for the filaments of the various tubes, as indicated. Another secondary 53 is connected to supply heating current to the cathode of the full-wave rectifier 59, the plates of which rectinor are connected to a third high voltage centertapped secondary E9 of the transformer 56. The cathode of the rectifier 5b, which is a 52.3 tube, is connected through a choke coil 6i to the plates of the tubes 21, 22, 23, 24, and for the supply of B current thereto. Opposite ends of the choke coil 55! are connected through condensers 62 to the ungrounded end of the resistance 53, which resistance is brid ed by a condenser 63 and connected to the center tap of winding 69.

The power supply to the primary of the transformer 56 is adapted to be completed or interrupted by a switch G l which is located between the primaries of the transformers and This switch is physically united to a switch 6-3 so that they open and close simultaneously. One side of the switch $5 is connected to the pole of a switch E5. The other side is connected to contact ill of a relay One side of the secondary cf the transformer is grounded. The other end is connected through the winding of a step relay G9 to a conductor '28. The ungrounded side of the sec cndary of the transformer 55 is also connected through the winding of the relay to a conductor H. The conductors lo and ii, together with a third conductor l2, constitute a cable '53 of any desired length. This cable maybe con.- nected to any desired number of remote control units i i, two of which are shown by way of example in Fig. 1. It is, of course, to be understood that the cable lS may comprise as many units it and a many branches asmay be d sired. Each unit it comprises three switches i6, and Ti, one side of each switch being grounded to the conductor '52. The other side of the switch ll is connected tothe conductor ii. The other side of the switch 76 is connected directly to the conductor it. The other side of the switch '65 is connected through a resistance "(8 to the conductor it. It will readily be understood that when the switch ii is closed, the electro-rnagnet of the relay G8 is energized and the pole of the relay 88 moves away from engagement with the contact 6'? and into engagement with the contact is. The contact 19 is connected to one of the poles 89 of the relay 68. The relay 69 includes a second pole 8i which is normally maintained out of engagement with a grounded contact 32 by a hook-like projection 83 on the armature. When the relay E9 is energized, the armature is moved so as to allow the contact Si to become grounded, and the projection 83 move the armature 32} out of engagement with the contact 8 and into engagement with the contact The contact 8% is connected to a contact of a switch ill. The contact 85 is connected to a contact 88 of the switch 88, to a contact 9% of the switch 8'1, and also to windings SI and 92 of the motor A conprovided with two grooves I46 which are adapted to receive a spring element I41, so as to hold the shaft I39 in its inward or outward position, as the case may be. At its inner end, the shaft I39 carries a friction wheel I53. When the shaft I3!) is in its outermost position, the friction wheel M8, which may have a peripheral portion or tire of rubber or the like, engages a shaft I49, which is also rotatably mounted on the plates I35 and I3I. At its forward end, the shaft I 49 carries a friction wheel I55 which is similar to the friction wheel I 48. The friction wheel I53 engages the hub I43 of the gear MI. The gear MI is connected through suitable speed reducing means, such as the gear and pinion II and I52 to a pinion I53, which is adapted to be driven by the motor 35.

The pinion I53 is shown on a large scale in Fig. 5. The pinion I53 is hollow and is slidably mounted on a sleeve I54 which extends inwardly towards the motor 36 from the core I of the relay I09. This relay is carried in front of the motor on the plate I33, with the sleeve I54 in axial alignment with the shaft of the motor. The pinion I53 carries at its outer end a disc I55 of magnetic material, which is adapted to be attracted by the relay I59 when its winding is energized. At its inner end the pinion I53 carries a clutch projection I51 which is adapted to engage corresponding projections I58 carried on the forward end of the shaft of the motor 36. The pinion I53 is normally biased inwardly by a spring I53 so that the clutch projections I51 and I58 tend to engage. The spring I53 is located in an axial recess I53 in the core I55. This spring applies pressure on a rod IGI which extends through the sleeve I54 and abuts against a hardened disc I52, which is located within the hollow pinion I 53 adjacent its innermost end. The degree of compression exerted by the spring I59 is controlled by a screw I53. It will readily be understood that immediately the relay IE9 is energized, the disc I 56 is very strongly attracted and is moved to the left, as viewed in Fig. 5. The pinion I53 moves with it, and likewise the clutch projection I5'I. Consequently, these clutch members are withdrawn from the clutch elements I58, and the pinion I53 is comgletely freed of any connection with the motor 0. and the disc I55, this complete disengagement occurs very rapidly and thedrive for the condenser is freed from the inertia of the motor armature. The magnetic force of the relay I39 also draws the disc I 56 strongly against the friction surface I55, thus applying a strong braking action to effect the quick stoppage of the pinion I53. The elements of the drive between the condenser and the pinion I53 are driven relatively slowly and have small moments of inertia, so that their inertia is not a serious problem, as will hereinafter be more fully described.

When the knob I38 has been pressed inwardly, the shaft I39=is driven directly by the gear I II through engagement of its hub MS with the pin I35. This adjustment adapts the receiver for ordinary station reception. For short wave reception, it is preferred to adjust the drive of the gang of condensers so that it operates much more slowly. This object is obtained by pulling the knob I 33 outward, whereupon the drive of the condenser occurs from the gear It! through its hub, the friction disc I55, its shaft M5, and the friction disc I48.

Owing to the small mass of the pinion I53 The rear end of the motor shaft I29 is provided with a pinion I66 which is connected through speed reduction gearing I with a hub I65, which is rotatably mounted on a bearing I 67. At its inner end the hub I55 carries a gear I58. The toothed wheel I58 is adapted to be engaged by a pin I55, which projects rearwardly from a detent wheel I13. The detent wheel I'IB is carried on the rearward end of a hub Ill, this hub being provided with a rigid abutment plate I12 which engages one side of the wheel I16, and a spring member H3 which resiliently forces the wheel I'Ifl against the abutment plate I'IZ. A shaft I'I l extends through an opening I in the frame plate I30. The shaft I'M is held against axial movement by means of collars IE5 rigidly mounted thereon on opposite sides of the plate I30.

The hub I "H is provided with opposed slots I'Il which receive opposite ends of a pin I'IS rigidly mounted in the shaft I13. A pin I79 projects radially from the hub ill so as to cooperate with a cam member I60, which may suitably be formed from a rearwardly turned portion of the plate I 33. The hub III is normally biased towards zero volume position of the volume control rheostat [ill by means of a spring I32. This spring is anchored to a stationary abutment I83 and to the pin I79. The shaft I74 extends freely through the hub I65 and carries at its innermost end one element I55 which cooperates with another element I35 of a universal joint mechanism. The member I55 is mounted on the shaft I 83 of the volume control rheostat Ifil. This rhecstat is supported by a bracket I31 from the fram mem ber I31. The frame member i3I supports the elements of the relay 53, previously referred to. The armature of this relay is provided with a detent member I 83 which is adapted to cooperate with the detent wheel I13. t will readily be understood that when the shaft I'M is manually actuated by the knob I239, the rheostat I8! is operated directly, the friction connection between the detent wheel I13 and the hub I'II enabling this Wheel to stand still in the position in which it is held by the detent I33. It will be understood that when the relay 88 is energized the detent I88 is withdrawn from the wheel Il'i and the spring I82 throws the shaft I'M around to zero volume position. Furthermore, if the knob I59 is rotated still further in the volume decrease direction, the switches 53 and 55, which are operated by the rheostat shaft 35, are opened. The friction connection between the wheel no and the hubs Ill and the engagement of the wheel I'Iil by the detent I33 insures the maintenance of any manual adjustment, until changed by further turning of the knob I59 or the energization of the relay It may here be re marked that the detent I88 comprises a portion which overlies the wheel I10 and a tooth or detent portion which enters between the teeth of the detent wheel I'IIJ. It will likewise be under stood that if the knob 39 is rotated in the opposite direction by hand, the switches 54 and 55 will be opened. The volume control rheostat ISI can, of course, be operated in either direction and the switches 54 and 65 turned on or off by the energization of the relay 58 so that it moves its armature upwardly as shown in Fig. 3.

Upon the shaft of the gang of condensers I provide two arms I90 and I9I which are adapted to cooperate with the operating arm I92 of the switch 89. These arms come into contact with the arm :92 as the condenser shaft attains its extreme positions. The actuation of the switch 89 reverses the motor so that the same tends to operate in opposite directions while the condenser moves between extreme positions. In actual operation, this back and forth movement is terminated when a station is tuned in which has sufficient volume to energize the relay I69 and disconnect the motor. it is to be understood that the switch 8'1 and the switch 85 may be omitted, if desired, the switch 65 being connected directly to the pole of the switch 38. The switch El is preferably employed so as to enable a different adjustable range of tunin or range of condenser control between points of reversal to be employed. For this purpose, I loosely mount on the shaft (3 an arm 293. This arm is adapted to be engaged by two studs 195 and 595 which are adjustable to vario lS positions in two arcuate slots and IS? in a disc E98. This disc is rigidly mounted on the shaft 133. The arm 193 carries a pin 1%, which is located in a slot formed by the forked end of an actua ing arm of the switch 8?. It will readily be understood that the position of the condenser at which the arm is actuated to reverse the motor can be controlled as desired by changing the position of the stuis ltd and 95 on the disc 538. A has been previously described, the oscillation of the motor and the condenser may be controlled either switch til or :39, control being transferred from one to the other by the mere actuation of the switch which may be located at any desired position.

The dial 223 of the indicating preferably translucent carries nations and numbers which may the various frequencies of broadcast band. The translum. dial 223 i illuminated by a plurality of lamps ra l on the reverse side of the dial. These lamps are mounted in a dish-shaped housing 225 which includes an annular shelf or flange 225 to which the periphery of the dial is secured in any suitabl way. Beyond the flange 225, the housing 225 is provided with an outer flange 22l'. This flange is displaced forwardly of the flange so as to provide a space on the outer side of the dial in whiz e pointer 22% is adapted to move. The pointer call is carried on the end The forward face of the housing device is suitabl gradcorrespond to +1 ufle the flange 22? by a gasket 232. The window is secured to the flange 2a? by means of a secui 1 rng which includes an outer flange 23 i adap ed to be secured to the flange 2*? means or" The securing ring is of step section, as best seen in Fig. 8. It includes a flange 23iwhich is adapted to bear against the window The inner portion of the 33%, which is indicated by the reference numeral 235, is displaced forwardly so that it is located out of contact with the window 23%. Between the displaced portion 235 of the flange and the window 233i is provided a space 238 which is adapted to r ceive tabs 23?. These tabs may be of transparent material, having a lightedbackground for opaque characters designating different broadcasting stations. The tabs 23'! are preformed into concave as best seen in Fig. To install a tab, it merely necessary to apply it to the glass 23i and slide it radially in the proper direction until its outer end is located in the nan recess to, as best shown in 8. The inner portion c: the flange 234 may be resilient and biased towards the windo. 23E As a result the spring l of the curvature of the tabs or the inward biasing of the portion 235, or both, the tabs 23? are firmly held in position. To adjust the position of a tab for a particular broadcasting station, it is only necessary to tune in that station and slide the tab circumferentially so as to bring the opaque graduation at the inner end of the tab in radial alignment with the pointer 223. The tabs may be removed when desired and they may be replaced by other tabs. Owing to the initial convex form of the tabs 23?, they lie quite iiat against the window 223i when installed. It is of course to be understood that the window 23H is located in anopening in the front wall of the cabinet 239, which opening is finished by a suitable bezel 2th.

The operation of this modification (as shown in l) is as follows:

The set is put into operation by pressing the button ll. This results in the'energization or the relay 68 and the withdrawal 01' the detent i353 from the detent wheel lit. The pole H3 of the relay GB is moved into engagement with the contact it. The motor circuit is then completed from ground through the pole H3, contact iii, pole to of the relay 6%, contact lid, motor windings {i i and and secondary of the transformer do to ground. When the motor is thus put into operation, the pin it'll resting on the elevated surface of the cam Ltd, the pin 969 is engaged with the wheel let. Consequently, the motor drives the shaft l'i l and consequently'the shalt 35 in the volume increasing direction. The result or the initial movement oi the shaft 86 in this 0 .1 rection results in the closing of the switches and 65. The closure oi the switch as imme diately energizes the heater circuits, including the heating element "Until the cathodes oi the tubes are heated up, the thermostatic element EZi holds the poles of the relay in their downward position, as shown in l. The motor 36 operates as long as the button 'ii is pressed, and when the button i! is released, the motor stops. When this occurs, the detent ml withdraws'the pin H59 from the wheel ltd. The detent locks the wheel ilil against rotation by The volume setting of the rheostat it! is thus maintained until the relay 68 is again energized. It will be understood that when the relay is deenergized, operation of the motorwili have no eiiect upon the volume control. Under these conditions, the motor will merely drive the condensers. When the heater has raised the thermostatic element iizi to a sufficient degree of temperature, the pole lit engages the contact ill, and the motor circuit is completed from ground through the pole his, contact pole its, contact tilt, switch at, switch "-a, one of the switches 8? or (dependmg on the position 01' switch through one or the pairs of field coils at, 92, or t l, of the motor, and secondary oi transformer 55 to ground. The motor will consequently start to operate in a direction depending upon the position oi the switch (or ill). Assuming that the switch 655 is in the relation shown in Fig. l, the switch 89 will have control. t will be understood that if the switch 8% is in engagement with the contact 93, the motor will start to move in the same direction as it did when the button 'i'i was -rst pressed. If, however, the switch 89 is in engagement with the contact 88, the motor will operate in the reverse direction. If no signal is being received by the set, the motor would continue to operate al ernately in opposite directions, the

arms iflt and IN engaging the arm N2 of the switch 89 so as to reverse the motor for such operation. When, however, a signal of adequate strength is received, the operation of the motor will be terminated in a manner which will now be described.

When a signal is received by the receiver, intermediate frequency energy is transferred from the primary of the transformer 39 to the winding 3?. It may here be pointed out that if signals on closely adjacent frequencies are to be tuned stop-on-carrier, it is desirable that there be the maximum difference in amplitude between the desired signal and other signals on closely adjacent channels. It is therefore preferable that the intermediate frequency transformer 38 from which the stop-on-carrier signal is obtained should be the last intermediate frequency transformer, that is, the one immediately ahead of the second detector. mary of the transformer and the winding 31 may be in the neighborhood of optimum coupling, or somewhat less. The coil 3? and the condenser 38 preferably form a high Q circuit sharply tuned to the intermediate frequency. An intermediate frequency signal in the tuned circuit of the coil 37 and condenser is impressed upon the grid of the tube 39. The negative direct current voltage applied to the grid of the tube 39 is suificienthigh to cut off the broader base portion of the intermediate frequency signal in the tuned cir- -cuit 3?, 38, so that the effective positive signal on the grid of the tube 3c is only as wide as that portion of the intermediate frequency signal which is of higher positive voltage than the negative voltage of the direct current signal. This produces an effective signal on the grid of the tube 39 which is extremely sharp. The sharpness of this signal is not substantially influenced by the coupling between the primary of the transformer as and the coil 3'1, and can be best increased by increasing the Q of the tuned circuit 3'1, 38. However, either too tight or too loose a coupling will undesirably affect the band pass characteristics of the transformer 39 and therefore the quality of the audible signal. This coupling should therefore preferably be adjusted so that the resonance curve has two peaks, with the single peak of the resonance curve of the tuned circuit 3'1 and 38 located midway between them, as shown in my copending application Serial No. 219,713 (Patent No. 2, 5 It has been found that for best results, the peak voltage of the intermediate frequency signal applied to the grid of the tube 39 should have a ratio of around 3 to 2 compared to the negative direct current voltage applied to the same grid from the diode element of the tube 25. When the sha p, positive intermediate frequency signal is impressed upon the grid of the tube 39, the current in the plate circuit of the tube 3s increases sharply. This plate current flows from the cathode of the tube 39 through the choke coil I23, the switch 124', and the resistance I25 to ground. The ungrounded end of the resistor H5 is connected to the grid of the tube 181. The condenser [26 serves as a high frequency by-pass condenser. The choke coil 23 serves as an anti-static choke coil which is effective in greatly reducing the tendency of brief pulses, such as static, to ionize the gas tube lei. Sudden surges, such as static, have a short duration, and the choke coil E23, the resistance I25, and the condenser E24 constitute a low-pass filter which blocks rapid impulses of brief dura- The coupling between the prition. At the same time, this filter passes sustained oscillations of longer duration or lower frequency which create a substantial voltage across the resistor I25 when a station of suitable strength is tuned in. This voltage being applied to the grid of the tube lill ionizes this gas tube, with the result that the relay I09 is energized. This energization results in the immediate arrest of the gang of condensers and the breaking of the motor circuit which occurs when the relay 53 is energized and the pole i i 4 is withdrawn from the contact H1. The condenser H2 is normally charged, owing to the voltage across the resistor l l I. When the tube I9? is ionized, the condenser H2 is discharged, with the result that a very large current flows through the winding of the relay I99 at the instant the plate current starts. Thus the condenser I I 2 materially aids in the instant arrest of the condenser.

It will be understood that when the condensers are thus arrested and the set is receiving a station, the relays 53 and it remain energized, due to the fact that the tube iii! remains in an ionized condition. When it is desired to tune in another station, the button 15 is pressed. The result is that the relay 69 is energized through the resistor 18. For the reasons previously described, this energization of the relay 69 does not affect the position of the ratchet wheel 99 and the cam wheel Hill. The movement of the armature is, however, sufficient to bring the pole 85 into engagement with the pole 82, thereby grounding the grid of the tube ltll. This deionizes and terminates the plate current of the tube W1, and the relays 53 and H39 are de energized. The pole li i moves upwardly into engagement with the contact H1 and thereupon the motor circuit is complete through the grounded pole H3, contact E57, pole Ht, contact iii, switch 65, switch 6", and one or the other of the switches 37 or 85. Consequently, the motor operates until a new station is tuned in in the manner described above. If the button 75 is held depressed, the motor continues to operate the condensers until the button 15 is released. If the button '36 is depressed, the same action occurs as has just been described in connection with the button 15. In this case, however, the energization of the relay 89 is much stronger, and the cam wheel i528 is moved one position. The net result'is that the grounded pole lfll is moved into engagement with the other contact 33 or iii-l; Consequently, the bias of the oathode of the tube I0! is altered and a different voltage is required on the grid of the tube I61 in order to initiate its operation, Thus, if the effective resistance N5 is larger than the effective resistance Hi8, then when the former is grounded through the pole 10!, it will require a higher voltage on the grid of the tube Iii! to put this tube into operation by effecting its ionization than when the resistance IE8 is grounded. Consequently, when the resistor I65 is effective, the set is adapted to respond to a smaller number of stations giving the strongest signals, and the resistor Hi8 responds to a larger number of stations, which includes stations giving weaker signals,

When the button TI and the button 76 are depressed, then the relays 68 and 69 are both on ergized and the motor circuit is completed through the grounded pole H3, contact 79, pole 85, contact 85, windings BI and 92, and secondary of transformer 55 to ground. Owing to the energization of the relay 68, the detent I88 will be withdrawn from the ratchet wheel ms. The spring 32 is now free'to rotate the hub ill to zero volume position, which results in its axial movement, owing to the engagement of the pin lid with the most elevated portion of the cam list. This axial movement brings the pin 69 into engagement with the gear its. The simultaneous energization of the windings 9i and 92 effects the drive of the motor in a direction to carry the shaft E88 beyond zero volume position in the volume reducing direction, opening the switches to and .65. If the buttons 76 and ii are held depressed after the final position of the shaft 553 is attained, the detent Wheel llii merely slips on the hub ill When the buttons re released, the relays E8 and G9 are de-encrgized and the motor circuits are broken.

It may here be remarked that the minimum time switch iil i insures the movement of the condensers from one tuning position to another upon he depression of the buttons '55 or it. If it were not for this switch, the buttons 75 or it might l e depressed for a very short time and the gas tube i8? might be ionized again by the voltage derived from the station-which it was desired to tune out. The centrifugal means which controls the switch insures sufficient rotation for the condensers to tune out one carrier before they can be arrested by the gas tube Nil, no matter how quickly the button ill or i8 is actuated.

When the set is in operation, the depression of the button ll results in the energization of the relay 63 and the elevation of the detent B88 from the detent wheel lit. When this happens, the spring H32 returns the shaft lit and shaft set to zero volume control position of the rheostat lei. The cam B6 effects the axial movement of the hub ill so as to engage the pin 69 with the gear 68. The energization of the relay 38 causes the motor circuit to be completed through the windings 53% and 95 so that the motor is put into operation in a direction to rotate the shaft 535 to increase the volume of the audible signal. During this operation of the motor, the is unaffected because the relay Hi9 and relay remain energized. When the button fl is released, the desired volume having been reached, the motor circuit is immediately broken, and the detent E38 engages and arrests the detent wheel fill and moves it away from the gear wheel The desired volume setting is maintoo, tained by the engagement of the detent 88 with the detent wheel lid until the relay 68 is again Ci a It is to be noted that during normal reception, the relay 53 is energized and the pole is separated. from the contact 5 3. When, however, the set is being tuned, the pole H5 is in engagement with the contact 52, thus groundng the grid of the power tube 25 and muting the set. When the set is in normal reception, the condenser H9 is grounded through contact lit and pole lib. Consequently, the automatic volume control voltage, which is applied on the grids of the tubes El, 22 and 23 through the resistance 25E, changes relatively slowly due to the time delay introduced by the resistance 2M and the capacityof the condenser H9. During tuning, however, at which time the relay 53 is deenergized, the ground connection of the condenser H9 is broken, with the result that the automatic volume control applied to the tubes just mentioned is substantially instantaneous, owing to the elimination of the capacity of the condenser are, providing what I prefer to call fast automatic volume control. This fast autoinatio volume control during tuning has several very remarkable advantages. 'In the first place, owing to its almost instantaneous effect, it domodulates received signals to a considerable degree and therefore reduces the difierence between the maximum and mimmum amplitude of the carrier frequency resulting from modulation. The result is that the signals are effective in arresting the condensers more on the average sig nal level of the carrier than on the peaks, due to modulation. In the second place, fast automatic volume control largely eliminates the passing over of a weal; station after leaving a strong station close to it. Thus, if the condenser M9 were grounded during tuning, its charge might persist for sufficient time to prevent the stopping on a weak station, the frequency of which was close to that'of the signal from a strong-station, which had previously effected the charging of the condenser. Finally, fast automatic volume control, owing to its practically instantaneous action, reduces the tendency of static or oth r un-- disturbances of brief duration from stopping the condenser during tuning. Ordinary automatic volume control, notwithstanding its time lag, may decrease the amplification of a relatively long or continuous signal to a high degree, While reducing amplification very little in the ease of pulses having sharp wave fronts or peaks of very brief duration.

The radio set illustrated in 2 is intended primarily for an automobile receiver. In general, the wiring diagram of the set is substantially similar to that illustrated in Fig. l, with the omission of one of the intermediate frequency tube 23 and the corresponding transformer 29. Consequently, corresponding numbers have been given to similar parts. It may be noted, however, that the connections to the loud speaker 2% are shown in Fig. 2, while they are omitted in Fig. 1.

The set comprises a vibrator 283 and associated transforming and rectifying means 26% adapted to provide the B supply for the tubes. Power is derived from a storage battery 29-5, which may be the battery of the automobile. As shown in Fig. 10, the loud speaker 2232 may be located in the roof of an automobile 295. The main portion of the set 2'! may be suitably located in the hamper of the car. This arrangement is particularly suitable for use with a rod type antenna 2%. Thus, the antenna may be mounted at the rear of the car and may be connected by a relatively short cable 299 to the set 2M. The set 29'! may be supplied with electrical energy from the battery 265 through a cable 2!, which may suitably include a grounded sheath. The arrangement of the set 207 remote from the engine and its high tension ignition system and adjacent the antenna 298 is remarkably suitable for satisfactory reception, since pick-up of objectionable disturbances from the electrical system of the car is substantially reduced. This is not only due to the distance of the antenna 298 from the ignition system, but also due to the fact that the metal body of the car acts as a shield between the ignition system and the antenna.

Suitable control devices 2! i may be provided. One of these may suitably be mounted on the steering Wheel column, preferably where it can be reached Without removing the hand from the wheel. The other may suitably be located in the back portion of the car for use of the passengers in the rear seat. In addition to the control units 2, I provide an indicating device 252 on the dashboard and a sensitivity control device 213, also on the dashboard. If desired, there may be included with these dash mounted devices a third control unit (not shown) for the convenience of the other occupant of the front seat. Each volume control unit comprises a single pole, double throw switch 225, which can be thrown one way or the other in order to ground a conductor 2 i G or a conductor 2 I! through the volume control relay 255'. It will be obvious that the switch 2E5 may be replaced by a pair of independent buttons or one-Way switches. The remote control unit 2H also includes a button 2l3 which can be depressed temporarily in order to ground a conductor am through the volume control relay 225'. The conductor H9 is connected to the grid of the gas tube Hill, which has the eliect of d8-l0l1iZll1g the ga tube and de-energizing the relays i239 and 223.

On the common condenser shaft which carries the rotors of the condensers 32, 33, and 34, I mount the slider of a potentiometer 22L One end of the potentiometer is grounded, the other being connected to the conductor 222. The slider of the potentiometer iii is connected to one terminal of the indicating device 2| 2, which is a current responsive indicator graduated in the frequencies of the broadcasting band. It will thus be understood that while the slider of the potentiometer 22! is located in the housing 282' in the hamper oi the automobile, the station to which the set is tuned is shown on the dial of the indicating means 212 on the dashboard.

The sensitivity control device 213 comprises a grounded arm 254 which is adapted to engage any of a plurality of contacts 242 on the dashboard. These stops are separated by resistances 253 and 24 i, and the latter is connected to an adjustable rheostat 2 55 which may be located in the housing 2M. The rheostat is connected to the cathode of the gas tube H3 1. It will readily be understood from the description of the previously described embodiment that the sensitivity of the tube l til may be given the proper general adjustment by the rheostat 2&5 and may be adjusted to receive local and distant stations, or only local stations, by the arm 2:. The effect of this rheostat and the arm 2 1! is, of course, to vary the relative grid bias of the tube 1 ill. The windings of the relays its and 22!] are arranged in series in the plate circuit of the tube I01, as were the windings of the relays IE9 and 53 in the previously described embodiment.

The relay 2% may be associated with a thermostatic element Hill which is adapted to hold the armature and the poles in the position they occupy when the relay is energized. The thermostatic elenient i2! is provided with a heating coil which is connected to the conductor which supplies current to the filaments and also to vibrato-r and rectifying unit when the conductor is connected to the ungroundeu s of the battery M6 by means of a switch i the switch 2 1i is closed, the filaments begin to warm up, and at the same time the heater H2 warms up. When the filaments are warmed up, the thermostatic member till is moved away from the relay with the result that this relay moves to its normal de-energized position under the action of the spring which is connected to its armature. The relay ltd-J comprises a pole ass which is connected by a switch 2-39 to .a switch The switch 2M is physically connected to the switch i i-l so that the two switches open and close simultaneously.

The switch 252? is adapted to connect to either of two contacts 725! and 252 of the motor 36. The contact 25:

233 oi the motor connected to one winding connected to the while the contact s52 is winding of the motor 35. The two contacts 255 and are bridged by a high resistance contact 26 l which is strictly analcinbodiinent, gives the necessary delay to the QcliiOlllfitlOVUllilll control bias applied to the tubes 23 and 22. During tuning, rat is, when the inc-tor is driving the condensers in search oi the next station to be tuned in, the pole iii-i8 is to d away from the contact 2425, with the restdt that fast automatic volume control is applied to these tubes. When the relay 223 is tie-energized, the pole 25?, which is ungrounded, engages a contact which is connected to a conductor The grounding of the conductor renders the set mute. When a station is tuned in, the relay is energized and the muting circuit is broken. The pole 2 .18 is adapted to engage the grounded contact 2134 when the relay is de-energized. When this occurs when the is turned on, the motor circuit is completed through grounded contact 264, pole sw"ch its, switch 2%, and either Winding or tel, commutator u, conductor 222i, and tcry to ground. The motor will be put into operation in a direction depending on the pc ion of the switch When the switch is in one position, for example, the position in which it is shown in Fig. 2, the field winding is energized and the motor turns in one direction. When the switch 2% is in engagement h the contact 2&2, the winding 254 is enersized and the motor turns in the opposite directicn. It will be understood that the switch 25;), like the switch ill or iii of the previously described embodiment, is actuated or reversed by the gang of condensers when the same arrives at an extreme position. Consequently, the condensers will be moved from one extreme position to the other continuously until a carrier is resolved with sufficient signal strength to energize the gas tube iill, whereupon the relays i519 and are energized, arresting the movement of the condenser and breaking the motor circuit established between the pole 2:28 and the contact 26 1.

The device just described with respect to Fig. 2 will be understood more iully in its physical embodiment, as shown in Figs. 10, ii, 12 and 13. The motor 3% is provided with a shaft 265 which carries a pinion 235 on its outer end. On the inner side of the pinion 2263, the shaft 265 is provided with a collar which serves as an abutment for a spring 283 located around the shaft and serving to apply friction, with the or" suitable washers, to a pinion 369, otherwise freely rotatable on the shaft 265. The pinion meshes with a gear which is pro- With projections Ell. The projections 2 are adapted to be engaged by one or more projections 212 on a pinion 2'43, which is mounted for slight axial movement in alignment with the gear 219. The pinion 213 is quite similar to the pinion I53 shown in Fig. 5,.which pinion is actuated by the relay I09 in the manner described above in connection with the first'embodiment. It is to be noted, however, that the relay I99 is located at an intermediate point of the gear train, which gear train comprises the elements 266', 210, 213, 214, 215, and 216, which is mounted on the shaft 211, which carries the gangof tuning condensers and the contact arm ofthe potentiometer 22I. The element 216 carries projections 219 which are adapted to cooperate with the arm 289 of the reversing switch 25%, previously described.

The pinion 269 is connected through a train of gear elements 2-82, 283, 284, 235; andZBE, to a shaft 289 of the volume control 292. The shaft 289 also controls two switches 241 and 229 mounted on the back of the Volume control 299, so that the set may be turned off by turning the volume control beyond the zero volume position in the volume decreasing direction. The train of gears 282 to 286 is adapted tobe arrested in definite position by means of the relay 2 I The armature 29I is normally pressed outwardly by means of a spring 292 so that its reduced outer end 293 is adapted to project between the spokes of the gear element 284.

The operation of this embodiment is as fo1- lows: The two-way switch 2I5 is thrown to one side, for example, to the left, as viewed in Fig. 2, so as to complete a circuit from ground through the relay 215', conductor 29 i, switch 215, con ductor 2I6, winding 254, conductor 2'46, and battery 255 to ground. This drives the shaft 289 in a direction to close the switches 241 and 249 and to increase the volume level. When the switch 2I5 is released, the motor is stopped. The battery now supplies current to the filaments through conductor 245, switch 241, and conductor 222. It may here be interposed that if the volume level is too high, it may be lowered by merely throwing the pole of the switch 2I5 into contact with the conductor 2I1, whereupon the motor is driven in the opposite direction until the volume level desired is attained. When the set is first turned on, the thermostat I2I is cold and maintains the poles 251, 258, and 243 in the position they occupy when the relay 222 is energized. Consequently, the motor cannot be actuated except by the switch 2I5, in which case the'relay 2I5 is energized. When the relay 2I5 is energized and the motor circuit is completed, the projection 293 of the armature 25H of the relay 2I5' is withdrawn fromthe gear 284, and the motor starting, the gear train 232 to 236 is efiective for driving the shaft 289. When the circuit of the motor through the volume control relay 2 I5 is opened by releasing the switch M5, the de-energization of the relay permits the spring 292 to thrust the armature 29! outwardly so that its projection 293 engages and arrests the gear 284. At the same time, the motor is do energized and the inertia of the armature is accommodated by the slippage of the shaft 265 rela-' tive to the pinion 269. The operation of the motor 36 changes the position of the gang of condensers and associated elements. If the gang of condensers is left so that no carrier wave is being received with sufiicientstrength to efiect the ionization of the gas tube I91, then the-relays IE9 and 22B are not energized so that the clutch elements 21! and 212 are in cooperative relation. Consequently, the motor, when itstarts, is adapted to drive the gang of condensers. The

motor goes into operation to drive-the condensers whenthe heater I22 has raised the temperature of the thermostatic element I2I adequately. The motor circuit is completed from ground through the contact 264,- pole 248, switch 249, switch 258, the motor 36, conductor 245, battery 225, and grounded conductor 2I9. During this operation, the condenser 259 is not grounded, and consequently, fast automatic volume oontrol'is applied to the grids of the tubes 21 and 22. When the condensers tune in a carrier wave of sufficient strength, the gas tube I01 is ionized and the relays I99 and 220 are energized. The energization of the relay I29 effects an immediate interruption of the drive of the gang of condensers, and the energization of the relay 220 interrupts the motor circuit and effects the grounding of the condenser 259. It will, of course, be understood that when the relay 229 is de-energized, the set is muted through the engagement of the pole 251 with the contact 292. When the relay 229 is energized, the muting circuit i interrupted by the downward movement of the pole 251, as viewed in Fig.2.

The-set being new in condition to receive a station if one of the buttons 2L8 is pressed, inwardly, the grid of the gas tube I91 is grounded and the tube is de-ionized. This grounding occurs through the Volume control relay 2I'5, but this relay is not actuated sinc only a negligible current flows. The de-energization of the relays I99 and 229' causes the mot-orto be put into operation and it remains in operation as long-as the button 2 I2 is pressed. When the button isreleased, the motor continues to operate until the condensers tune in a stationof-sufficlent signal strength to ionizethe tube Hi1. This ionization is efiected by a positive'voltage applied to the rid of the tube through the switch I25, which is controlled by a governor or other timing device, such for instance, as that described in connection with the previous embodiment.

I have found it to be advantageous to locate the clutch elements 21! and 212, together with the'contrcl relay E29, at an intermediate point of the gear train between the motor pinion 255-2 and the'gear 216 driving the gang of condensers; At the low speed end of the'train, the torque transmitted by the clutch is high, andthe clutch lements-would require a larger amount of energy forjquick disengagement. On the other hand, at the high speed end of the train, the torque is small but the energy of rotation of the clutch members which remain connected to the condensers after the clutch is disen-gagedis high. As a matter of fact, this energy of rotation increases with the-square of the speed and tends to Drolong the time between the disengagement of the clutch-and the stoppage of the condenser. For quickest condenser stoppage with reasonable clutch operating forces, a location of the clutch at an intermediate point of the gear train is highly advantageous. It is alsodesirable to decrease as far as practical the energy of rotation of all the partswhich remain connected to the condenser shaft211 and 'rotate therewith' after the clutch is disengaged. Those elements, such as the gear 212, which are disconnected from the con-densershaft 211, after disengagement do not contribute, to the continued rotation of the condenser; therefore their energy of rotation may be disregarded. I

In Figs. 14, 15, and 16, I have shown a modified clutch arrangement operated by the relay H92.

gear 214 of the last'described embodiment and the gear 291 corresponds to the gear 210. The.

gear 298, which meshes with the gear 296, corresponds to the gear 213. The hub of the gear 291 carries one or more projections 299 which are adapted to be engaged by an arm 390 rigidly carried on the end 3IJI of the shaft member 302. The end 31H is round and has a bearing 303 in a plate 334. The plate 304 is rigidly mounted upon and in spaced relation to a plate 335. The plate 305 is provided with a bearing 303 for the enlarged portion 301 of the shaft member 302. Between the enlarged portion 301 and the end portion 30!, the member 302 is provided with an intermediate portion 308' which is of non-round exterior shape. It may be quare, as shown in Fig, 16, and it extends through a bore 339 of corresponding shape in the gear 298. The gear 293 is located between the two plates 304 and 305, and the member 332 is freely movable within it in longitudinal direction. Between the plate 364 and the arm 333 a conical coil spring am is situated which urges the shaft member 302 normally to the right, as shown in Fig. 15, pressing the rounded end 3! against the flat center portion of the hub of the gear 281. It may here be noted that the gear 291, the member 392, and the pole of the relay I09 are in axial alignment. The end of the enlarged portion 301 of the member 3112, that is, the end which is normally located adjacent the pole 'of the relay I09, carries a frustro-conical head 3I3 of magnetic material. This head flares outwardly'from the enlarged portion 331 and terminates in a large flat face, 0.)

thin at the periphery, located quite close to the pole of the relay I39. as shown in Fig. 15.

When the relay I GSis not energized, the elements just described have the relation "shown in Fig. The spring 3H1 forces the end portion of the shaft member 3M into contact With the hub of the gear 291. A friction washer 3.II made from material such as Bakelite surrounds the pole piece of the relay I09, projecting a few thousandths of an inch beyond the face 3I2 .of the pole piece. When the head 3I3 is'attracted by, the energization of the relay I03, it bears upon the surface of the washer 3I l and does not make contact with the pole face. remaining separated from the face 312 of the pole piece by a small air gap. The washer 3II constitutes an effective braking surface against which the rotationof the head 3I3 of the shaft member 332 is effectively braked when the relay I08 i energized.

In this embodiment of the invention, part of the gear train of the tuning control is common to the gear train of the-volume control, both trains including the motor pinion 266 and the gear 291. The pinion 382. which is integral with the gear 291 meshes'with a gear 383 mounted for free rotation on a stub shaft 384; Upon the shaft 384 is mounted a pinion 385 which is adapted to be moved on the shaft towards the gear 383. The gear 333 is provided with a plurality of proiections 3851 directed towards the side on which the pinion 385 is located. The adjacent end of the pinion 385 carries an arm 381 which is adapted to engage one of the pins 386 when the pinion 335 is moved to the left, as viewed in Fig. 14. This movement of the pinion 385 is eifectedby a rod 38I which abuts against a disc 388, rigidly mounted in the end of the pinion 385 remote from the gear'383. The rod 38I is mounted for axial movement in a support 389. The rod 38I is moved to the left, as viewed In these figures, the gear'296 corresponds to the:

in Fig. 14, when the volume control relay 332 (Fig. 17) is energized. The relay 2I5' may also be adapted to operate the rod 331 when energized, if it is desired to employ the volume control clutch shown in Fig. 14 in connection with the embodiment of the invention illustrated in Figs. 11, 12, and 13.

In the embodiment of the invention illustrated in Fig. 17, which like Fig. 1, is adapted to operate from an alternating current supply, an intermediate frequency tube is indicated by the reference numeral 24. This tube is coupled through the transformer to the diode detector and first audio frequency amplifying tube 23, the relation of the tubes being substantially similar to the relation of the corresponding tubes in Fig. 1. A winding 31, which is closely coupled to the tuned secondary of the transformer is connected to the first grid of the double triode The first plate circuit of the tube 325 includes a, sharply tuned high Q circuit comprising a winding 32I and tuning condenser 322, by means of which the plate circuit is tuned sharply to the intermediate frequency. The Winding 32! is coupled to a winding 323 which is connected to the second grid of the tube 323. The winding 32I is also coupled to a regenerative coil 324, which is connected to the first cathode of the tube 32 and serves to feed back energy from the plate circuit to the grid circuit'of the first triodeele" ments of the tube 320. The regenerative coil 32 is connected through a condenser 325 and adjustable rheostat 325 to ground. The rheostat 326 is adjusted to prevent oscillation while providing the desired regenerative feedback. The second set of triode elements of the tube 323 are analogous'to the tube 39 of the first described embodiment. Regeneration is employed in this arrangement to increase the Q and therefore the selectivity of the stop'on-carrier tuned circuit. The double triode arrangement is employed to prevent coupling between the regenerative stopon-carrier circuit from adversely influencing the by-pass characteristics of the transformer 39. A single triode, as shown for instance in Fig. 1, may of course be employed with the control circuits of this embodiment of the invention. The cathode of this tube is connected to an inductance I23 and resistance I25 to ground. The inductance I23, resistance I25, and condensers I24 and I26 have the'same relation and function in a similar manner to those of the previous embodiment. The inductance I23 and resistance I25 are connected to the grid of a gas tube I31. The power supply includes an auxiliary transformer and a power transformer 53. The pri mary of the transformer 55 is controlled by a switch 64. This switch is physically connected to a switch so that these switches open and close together and are mounted on and actuated by the volume control. These and the other elements of the power supply unit are similar to those of Fig. l and are indicated by the same reference numerals.

The set may include a remote control unit similar to that of the first described embodiment. This unit may comprise switches 15, 15, and 11. The switches may be connected to a common wire 12, which is adapted to be grounded through a switch 321. The other side of the switch 15 is connected to the other side of the switch 16 through a resistance 13. Said other side of the switch 16 is connected by a conductor 18 to a re1ay328 and to a contact 329. The other side of the switch 11 is connected through a conductor accuses "H to a relay 332 and to a pole 3330f a double pole switch which includes 1a pole 334 mechanically connected to the pole $33. The exterior portions of the three conductors to, ll, and 12 may be formed into a cable :and be connected to the set by means of-a plug 335 which is adapted to be inserted in a receptacle 336. The remote controlmay be removed from the set by merely withdrawing the plug 33-5.

t will readilybe imderst'ood "that a plurality of units l i may be employed'i'fdesired, the corresponding elements being merely connected in parallel, as shown in Fig.

The switch 323 is a single "pole switch adapted in one position to connect the conductor 22 to ground. This switch is physically connected to the switch 336' which is adapted, when the switch 321 is open, to connect conductor 33:? to contact 338 of the relay 323. One side of the secondary of the transformer 55 is connected to the winding of the relay 332 and to the relay 3 23. One side of the switch lit is connected to the pole 339 of relay etc. The other side of the switch 651is connected to contact 345 of relay 332,

A switch pole 342, controlled manually by a button 353, is normally in engagement with a resilient contact 3M. When. the button 363' is pressed inwardly, the pole 3 32 is moved away from the contact 3%. When, however, the button 343 is :pulled outwardly, that is, downward ly, as viewed in Fig. 17, the contact 3 14' is brought into engagement with the contact 329. The contact stills connected to a pole-3% which is normally in engagement with the-contactatil. When the relay 323 is energized, the pole 3% moves away from the contact 338-. Th'epole342 is connected to a contact 346 which is normally engaged by the manually operable two-Way switch pole 347. tained in neutral position, as shoWn in-Fig. l-'l, by means of springs 3&8. The switch pole 3 11 is grounded. When'the'switch pole-3 4 is thrown in one direction, it is brought into engagement with the contact 3 59, which is connected to the contact 's, associated with the po1e333. When, however, the switch pole 34 1 is thrown in the other direction, it is brought into engagement with contact 351, which isconnect'ed to a contact 353, also associated with the pole 333. The contacts 338 are also connected to contacts 353 and 3152. An arm 33!, moving with the shaft of the gang of condensers, from which insulated, is adapted to engage contacts 333 at each end of the condenser travel, automatically reversing the direction of the condenser travel. The arm 33! is connected through a switch 53 to a contact 65!, which is normally "engaged by the grounded pole 386. The switch 35% is mechanically connected to the switches and 55 so that the contacts cannot be grounded when the relay'SSZ is energ zed-or the switches 3' 2 and 55 are open. The secondary-of the transformer 55 is connected to both windings 353 and 354 of the reversible motor which actuates the tuning condensers and also the volume control. The windings are connected to a contact 355 on one side of the pole 33%. 'The windings .554 are connected to a contact 355 on the other side of the pole 33 1. The armature of the relay 332 carries a finger 355' which is adapted to cooperate with a ratchet Wheel The ratchet wheel 35-? is rigidly-connected to a cam wheel 358 which is provided with a series of alternating recesses and projections; The

The switch pole 347 is meincam wheel is adapted to. cooperate with a cam member 35% carried by the pole 33 6. Each time the relay 332 is energized, the cam wheel Bot-is tuned one step, moving 'the projection 353 from a hump on the cam wheel into a recess on the cam Wheel, or vice versa. Consequently, the poles and 334 are moved alternately from a position in which tl iey engage the contacts 350 and 355, respectively, to another position in which they engage the contacts 352 and 356 re spectively, and vice versa. On each-energization of the relay 332, the pole 3th engages the contact Set-and may immediately separate there from; The armature of the relay 338 is provided with a projection-36! which is adapted'to engage a ratchet wheel 3552 in the same manner astthe projection 355' engages the ratchet Wheel 35 5. The ratchet wheel 352 is rigidly connected to'a Wheel which is similar to the cam Wheel 353. This cam wheel cooperates with a projection 3154 on a pole 365. The 'pole 335 is rigidly connected'to' a pole 365, When the projection 35 1 is received in a recess in the cam wheel 333, the pole 35% engages a contacttfil which contact is connected to an incandescent lamp 353. The other side of the incandescent lamp and the'pole 3% are connected to the filament supply, and it will'readily be understo'cdv that when the cam Wheel 363 isin the position in which it is shown in Fig. 17, the lamp 363 is illuminated. It shines through a Window 35-53 which may include a layer of translucent material 31o. This material may, for example, be WhiteCelluloid. Oh the rear side of the sheet 379 is a layer of colored material Sll, whic" may bored. This layer carries, suitably in'black or in letters of contrasting and pr ferably opaque color, a suitable indicating legend, such as the word distant. On the front of the layer 3H3 is carried another suitable legend, such as the word local. l his legend should be translucentand have the same color as the layer 3H, namely red. It will readily be understood that when the lair-113 398 is lit, the legend distant appears to the observer, the legend local be ing obscured by the general background of the same color. When, however, the 1arnp368 is not lit, the rear legend distant is not seen, and only the front legend, for example, local is seen by the observer.

The gas tube I81 has associated with it resistances 1635, I36, I38, and H1, and condenser H2, in the same relation as described in connection "with the first described embodiment. The resistance m5 is adapted to be grounded in one position of the cam wheel 353 through contact 372, pole 335, contact 338, pole 345, contact 34 4, pole 3 12, contact 366, and pole 3 H. When the camwheel 3'63 occupies its other position, that is, the position shown in Fig. 1'7, the resistance 108 is grounded through contact 3'13, pole 365, and other connections, as before. noted that one or the other of these two resistances is grounded at all times except when the relay 328 is energized, or when the button 343 is pressed, or when the pole SM is out of engagement with contact 345.

The pole 339 of therelayll-lll is rigidly connected' to the grounded pole 314; A thermostat 3T5 keeps the pole 339 and 314 in the positions.

they occupy when the relay 349 is energized. The thermostat 375 is controlled by a heater winding- 316 which is connected to the filament supply and is turned on when the switches '64 and 65- are closed. When the relay 340 'isenergizedthe It is to be pole 339 is moved away from the grounded contact 311 and the pole 314 is moved into contact with the contact 318, which is connected to the automatic volume control delay condenser 319, which operates in the manner hereinbefore described in connection with the corresponding condensers H9 and 259. At the same time, the pole 314 is moved away from the contact 380, making the signals audible which were muted during tuning in the manner hereinbefore described. Assuming that the switch 321 is connected to the conductor 12, that the switch 336' is opened, and that the cable 13 is connected to the set, then if the set is out of operation, the switches 64 and 85 are opened and only the transformer 55 is energized. The set is put into operation by pressing the button 11, whereupon a circuit is completed from ground through the switch 321, conductor 12, switch 11, conductor 1I, relay 332, and secondary of the transformer 55 to ground. The movement of the armature of the relay 332 moves the pole 390 into engagement with the contact 34I, thus completing a circuit through the motor 36 and through one or the other of the contacts 355 or 358 which is engaged by the pole 334. If the resulting rotation of the motor does not start the set, the button 11 is released and pressed again. This actuation results in changing the pole 334 into engagement with the proper contact to start the set. When the relay 332 is energized, the clutch for the volume control is put into engagement by the rod 38I and consequently the operation of the motor in the proper direction closes the switches 64 and 65 and continues to I turn the volume control in the direction to increase volume as long as the button 11 is pressed. The button is released as soon as the switches 64 and 65 are closed. Then, as soon as the filaments of the tubes are heated, the volume may be adjusted to the proper level. If, at any time, the volume level is too high, it can be lowered by merely pressing the button 11 again. If too low, the button 11 is again pushed. This actuation results in the fact that the pole 334 is moved to the right or to the left by the cam wheel 358 on each actuation of the button 11. The closure of the switch 34 results in the energization of the filament supply. Until the filaments heat up, the

thermostat 315 holds the pole 339 out of engagement with the contact 311, and the motor cannot be put into operation except by the button 11. When the heater 316 has warmed the thermostat up, the pole 339 moves upwardly into engagement with the contact 311 if the set i is not receiving a signal sufficient to maintain the tube I01 ionized. Consequently, the motor is gized. The energization of the former opens the motor circuit and. the energization of the latter declutches the condenser drive and applies a brake. The tube I 91 remains ionized while the station is being received. When the button 15 is pressed, a circuit is completed from ground through the resistance 18, the relay 328, and the secondary of the transformer 55 to ground. The energization of the relay 328 moves the pole 345 away from the contact 338, thus breaking the circuit which connects resistance I85 or I08, de-

pending upon the position of the pole 365, to ground. It will be readily understood that when this ground connection is broken, the voltage of the cathode of the tube I01 attains a high positive value corresponding to a high negative grid bias, the plate circuit is broken, and the tube is de-ionized. The de-ionization of the tube I01 causes the relay I09 to relax the brake and engage the clutch, and causes the relay 349 to complete the motor circuit. The direction of rotation of the motor depends upon the position of the pole 334. If it is desired to reverse this direction, it is merely necessary to close the switch 11 for the shortest possible time. This will have no appreciable effect upon the volume level. It is here to be noted that the energize,- tion caused by the button 15 is insufficient to cause actuation of the ratchet wheel 332. If the button 16 is depressed, it has the same eifect as the button 15 as has just been described, with the addition that the cam 353 is moved one step and the circuit connecting the plate of the tube 131 to ground is changed from resistance I05 to resistance I08, or vice Versa, changing the sensitivity of the stop on carrier tuning system. At the same time, the incandescent lamp 368 is either extinguished or lit, as the case may be.

The energization of the relay 332 displaces the rod 38I which controls the volume control clutch in the manner described in connection with Fig. 14. During normal operation of the device, to change from station to station, it is merely necessary to push momentarily the button 15. When the condenser shaft I 34 reaches the end of its travel in either direction, a circuit is completed through the relay 332 by the contact 33I, which moves with the condenser shaft 334, engaging one of the contacts 330, thereby producing the same effect as if the button 11 had been pressed momentarily. The result is that a circuit is completed through the relay 332 for a short time, which has the effect of reversing the motor, the motor current being passed through the windings 353 or windings 354, depending upon the position of the pole 334. If it is desired to reverse the movement of the condenser shaft I 34 at any time, it is merely necessary to press momentarily the button 11. V This changes the location of the pole 334. This enables a user to go back immediately to a station which he has just left. All he has to do is push the button 11 momentarily and then the button 15 momentarily. The rotation of the tuning condenser or other type of variable reactance is controlled by the relays I09 and 340. The volume control clutch actuated by the rod SM is operated by the relay 332, and may suitably be of the construction illustrated in connection With Fig. 14 or Fig. 18.

The manual controls 343 and 341 on the receiver are adapted for operation of the set without the aid of the remote control unit 14. Thus, if the button 343 is pressed, the cathode circuit of the tube I01 is broken and the tube de-ionized. The result is that the relays I09 and 340 are de-energized so that the motor circuit is completed so as to drive the condensers. When a signal of adequate strength is received, the buttons 343 having been previously released, the tube I01 becomes ionized and the resulting energization of the relays I39 and. 34!) stops the condensers in tune with the received carrier. When the switch 341 is moved away from its intermediate position into engagement with one ofthe contacts 349 or 35I, the cathode circuit is likewise broken and the motor tends to go into operation in the

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