US 3540344 A
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United States Patent Robert D. Veech 11 Yates Ave., Commack, Suffolk County, New York 11725  Inventor  AppLNo. 784,529
 Filed Nov.29,l968
Continuation-impart of Ser. No. 549,967, May 13, 1966, abandoned  Patented Nov. 17, 1970  MINIATURIZED METRONOME WlTI-I EARPl-IONE AND VOICE AMPLIFIER 12 Claims, 4 Drawing Figs.  U.S. Cl 84/484; 58/130  Int. Cl .f. ..G04b 21/00  Field of Search 84/484;
58/I30E, 22.9, 39.5, 152: 325/!(C0nsulted)  References Cited UNITED STATES PATENTS 2,924,705 2/1960 Jones .4 325/361 2,963,577 12/1960 Errichiello etal. 325/361 3,005,919 10/1961 Dias 307/1414 3,093,914 6/1963 Bernstein 3,112,446 ll/1963 Wilson OTHER REFERENCES Garner, A Transistor Metronome Radio and Television News, pp. 50, 5l,and 150, January 1954. Primary ExaminerStephen J. Tomsky Assistant Exanziner- Lawrence R. Franklin Artorney- Edward Halle ABSTRACT: This invention relates to timing devices, and more particularly to an electronically actuated metronome made of components small enough to be housed in a pocketsized casing including a loudspeaker and adapted to be used: with an earphone through a jack with loudspeaker cutoff so that the device may be personalized to the user without creating a disturbance to others. There may also be further switching means to include the loudspeaker within the circuit even when the earphone is plugged in; a plugin timer; and a plug-in amplifier connected through earp'hone plug jack means so that the instructor or other person may use the loudspeaker of the device as a microphone to give instructions or the like to a large orchestra or to a class and thereby amplify his voice by means ofthe device,
Patented Nov. 17, 1978 Sheet .I of 2 1 N VEN'IUR.
ROBERT D. VE ECH B YZOKUG/gg' T ZIQNE Y Patented Nov. 17, 197% Sheet 1 N VEN TOR.
284 25 ROBERT D. VEECH Bgvgwcwi H k ATTOR/VEX MINIATURIZED METRONOME WITH EARPIIONE AND VOICE AMPLIFIER This application is a continuation-in-part of co-pcnding application for MINIATURIZED METRONOME WITH EARPI-IONE filed May 13, I966, Ser. No. 549,967 and now abandoned.
In the prior art, the usual tempo indicator or metronome comprised an oscillating steel rod worked by a clockwork mechanism pivoted with a weight arrangement to vary the number of oscillations ofthc steel rod to increase or decrease the tempo. Recently, metronomes have been made in which the tempo beat is provided by electric or electronic means. Thus, mctronomes and tempo indicating devices are well known in the prior art and need no further description as to their functioning and usage.
The present invention proposes to provide a miniaturized metronome capable ofbeing carried in a shirt pocket or jacket pocket of an individual, or hung from a neck strap, and having an ear plug type earphone which may be placed in one of the ears of the individual so that the audible beat produced by the mechanism ofthe metronome can be heard only by the person using it.
Briefly, the invention is made with a circuit to be described hereinbelow and encased in a casing approximately the size of a package of cigarettes. having an ear plug earphone attached to it as well as a small loudspeaker when it is desired to use the metronome for anaudience of more than one.
The invention has the following purposes and advantages. The earphone will bring the pulsation of the metronome into intimate contact with the ear of the performer or student. The problem with existing metronomes is that the beat is remote because the metronome stands on the music stand, or table, or piano remote at a distance from the performer. The purpose of the metronome is to establish an example of a particular speed or beat upon which the tempo of the composition is based. Students consistently tend to ignore a remote beat when the difficulties of the music become so great that their sole concentration must go into the performance ofthe music.
The earphone of the invention permits the student to hear the music he is performing, and at the same time delivers a personalized intimate pulsation within his ear. The use of the earphone is also less distracting due to its intimate nature as compared with the visual distraction of a mechanical metronome or the remote audible clicking sound of an electronic metronome. Thus, there is no visual or audible distraction in the room.
A further advantage is that the metronome may be used by the leader of a large orchestra to obtain the beat with the earphone without distracting the orchestra or the audience. In addition, the metronome may be used by an organist during a church service with the earphone without distraction to the service.
Another advantage is that provision may be made for the instructor to listen to the heat through the loudspeaker of the device while the student listens to the heat through the earphone, permitting the instructor to monitor the students performance for accuracy in relation to the heat.
A further advantage lies in the fact that this metronome can be made extremely compact, the size of a package of cigarettes or'even smaller, so that it can fit into a shirt pocket or a purse or instrument case ofthe user.
Still a further advantage lies in the fact that the metronome can be attached to an amplifier by means of a connection through an earphone jack so that the output ofthe metronome can be broadcast to a larger area such as a complete symphony orchestra or a large classroom, and the instructor or teacher or leader may give instructions to the large group by speaking through the loudspeaker of the device which is thus adapted to act as a microphone.
The invention is battery operated and may have a neck strap as well as an optional hand carrying strap, and it may be put to other uses. Forexample, student typists may use it to develop a rhythmic typing beat. It may also be used by track and field runners to develop a timed pace, and it may be used in any type of activitywhich requires a graduated pulse or beat as a guide. 'I'hcinvention is also particularly useful in classes for the instruction of typewriting as each student may pace himself personally without regard to the different speeds of the students of the rest ofthe class.
The invention is illustrated in the accompanying drawings in which:
FIG. I is an exploded perspective view ofthe device;
FIG. 2 is a circuit diagram of the device with the earphone coil 44 dotted in to show its position when the earphone plug is fitted into the earphone jack means ofthe device;
FIG. 3 is an exploded perspective view, partly in diagram, of an alternate form ofthe device; and
Hg. 4 is a circuit diagram of an alternate form of circuit for the device.
Similar numerals refer to similar parts throughout the several views. 7
The pulse or beat produced by the invention which is adapted to be varied for a range of tempos between 40 and 208 beats per minute is produced by means of an electronic circuit as illustrated in FIG. 2 of the drawings. The circuit comprises a PNP transistor 10, a NPN transistor 12, a capacitor 14, a variable resistor 16, a trimming resistor 18, a speaker 20, an earphone jack 22, an earphone plug 23, an earphone 44, a power source such as battery 24, an On-Off switch 26, a monitor switch 25, and a fixed resistance 43.
The power source or battery 24 is connected through a conductor 30 to the speaker 20. Conductor 32 connects conductor 30 to the emitter ofNPN transistor 12. Speaker 20 is connected to earphone jack 22 by means of a conductor 36, and earphone jack 22 is in turn connected to the collector of the PNP transistor 10 by means ofa conductor 38.
The earphone jack 22 comprises a speaker cut out switch 27. When plug 23 is inserted into jack 22, switch arm 29 is moved away from contact 31 thereby removing the speaker 20 from the circuit as the earphone 44 is placed into the circuit by means of plugging plug 23 into jack 22. When plug 23 is removed from jack 22, current will flow through the speaker 20 which will produce an audible signal. On the other hand, when plug 23 is plugged into jack 22, the speaker will be silent and the current will flow through the earphone 44 to produce an audible signal in the earphone. It may be desirable for an instructor to monitor the performance of a student during such time as the student is listening to the metronome through the earphone. I have provided a monitor switch 25 for this purpose which puts the speaker 20 back in the circuit making it audible along with the earphone 44. Monitor switch 25 is connected to conductor 38, and the other side of monitor switch 25 is connected directly to speaker 20 by means ofconductor 41 and added resistor 43. Resistor 43 is added to balance the circuit when both the earphone 44 and the speaker 20 are operating. Thus. when monitor switch 25 is closed, the student will be listening to the beat through the earphonc 44 and the instructor will listen to the same heat through the speaker 20 and will be enabled to check and see whether the student is following the beat correctly.
Conductor 34 connects'capacitor 14 to conductor 38 at junction point 46.-The base of PNP transistor 10 is connected to the collector of NPN transistor 12 by means of conductor 48. Capacitor I4 is connected to the base of NPN transistor I2 by means of conductor 50 through junction point 52 and through conductor 54 and also to the variable resistor 16 through conductor 56. Variable resistor 16 is connected in series to trimming resistor 18 by means of conductor 58. The trimming resistor 18 is in turn connected to emitter of PNP transistor I0 through conductor 60, junction point 62 and conductor 64. The circuit is completed through conductor 66 to switch 26 which in turn is connected through conductor 68 back to the battery or power supply 24.
The circuit components as described hereinabove are adapted to be combined together and placed in an extremely small housing such as the one illustrated in FIG. I. A speaker 70 is mounted within the housing 72 behind a suitable speaker 3 grille 74. At a portion of the housing a dial 76 is rotatably mounted on a shaft 78 connected to the variable resistor 16. The device as illustrated in FIG. 1 is substantially the same size I as an ordinary package of king size cigarettes. The dial 76 is calibrated for the desired range of tempos, for example, starting from 40 beats per minute to 208 beats per minute. I
,prefer to have dial 76 substantially flush with surface 80 of housing 72 so that when the metronome is placed in and out of the users pocket,'the dial will be least likely to be moved. The dial 76 may also have a knurled edge 82 which may be reached by the thumb or fingers. The ()n-Off switch 26 is operated by dial )4 and the monitor switch is operated by dial 98.
1 also provide an eyelet 88 through which a neck strap 90 may be fastened to facilitate the wearing ofthc device around 1 the neck of the user, and 1 may also provide an optional carrying strap to enhance portability of the device, or the entire device may he made in a housing 72 adapted to be fitted into a case having a neck strap and/ora carrying handle.
OPERATION OF THE DEVICE the parallel branches comprises the loudspeaker means branch with loudspeaker 20, conductor 41, fixed resistance 43 and monitor'switch 25. The other branch is the earphone jack means branch which starts at first mentioned junction point 100, through conductor 36 to jack means 22 including earphone means 44, movable jack contact 29 to second mentioned junction point 102. Between these circuits there is a conductor 104 which is connected between loudspeaker means 20 and switch means 25 to a switch contact 31 which is a part of the normally closed loudspeaker cutoff switch means Thus, when the earphone plug 23 is not fitted into jack 22. the current will normally run through junction point 100. loudspeaker means 20, conductor 104, switch means 27 to junction point 102. When plug 23 is placed in jack 22. switch 27 will he opened cutting off loudspeaker means 20, current then flowing through junction point 100, conductor 36, jack 22, earphone 'means 44, movable jack contact means 29 to junction point 102. When it is desired to monitor, switch 25 is closed putting both branches ofthe' circuit into operation with current flowing through earphone 44 as just described and also through junction point 100 to loudspeaker means 20,
conductor 41, fixed resistor 43, closed switch means 25 to 'junction point 102.
In FIG. 3 of the drawings, 1 show an alternate form of the device which may be provided with a circuit as shown in FIG.
'- 4 of the drawings. The device of FIG. 3 is particularly adapted of the NPN transistor 12 drops thereby cutting off the NPN and PNP transistors and allowing the capacitor 14 to charge up. When the capacitor 14 is charged, the sequence of events previously described is repeated. The discharge of the capacitor 14 through the speaker 20, or the earphone 44, causes the speaker or earphone to produce an audible click. The frequencyof this clocking is determined by the resistancecapacitance relationship..By adjusting the variable resistor 16, the resistance-capacitance relationship .is changed which thcrchy causes a change in the frequency of speaker clicks. By attaching a calibrated dial 76 to the variable resistor 16, the frequency ofclicks can he read directly from the resistor dial.
in order to maintain a high degree of accuracy, a trimming resistor 18 is placed in series with the variable resitor 16. This permits a factory adjustment so that variances in the manufacture of components can be compensated for and the dial indicating frequency will be accurate and uniform from unit to unit.
In the event of a malfunction of the metronome, after a 7 period of usage, due to a burned out or faulty resistor, capacitor or speaker, the-faulty component may be replaced and the metronome can bcrecalibrated byadjustment of the trimming resistor 18.
The preferred circuit of the invention comprises a 9 volt battery power supply, a PNP transistor 10, similar to 2N 107 or 2N2l8, a NPN transistor 12, similar to 2Nl70, a 10 ohm speaker and a l0 ohm earphone, a 500K potentiometer for variable resistor 16, a 250K potentiometer for trimming resistor 18, an 8MFD capacitor 14, and a 30 ohm fixed resistance 43. These pcrametcrs are given as illustrative to show components which will work in the invention. However, any electronic oscillating circuit with variable resistance to produce a metered tempo signal in either a loudspeaker or earphone, and in both together, can be used. It is to be understood that the monitor switch 25 together with the fixed resistance 43 are optional parts of the circuit, and may be eliminated ifit is not desired to have the monitoring feature.
When the monitoring portion of the circuit including monitor switch 25 and fixed resistance 43 are included, the circuit in effect is provided with two parallel branches between a first junction point 100 an a second junction point 102. The first of to giving instruction in typewriting asit provides a metronome beat for the typist which may be heard personally by the typist through the use of earphone plug 23 and earphone 44, and the device of FIG. 3 represented by reference numeral 200 is provided with a self-timer 202 having timer plug 204 connected by means ofcable 206. Timer plug 204 is adapted It) be placed into jack means 208 to introduce the timer 202 into the circuit of thedevice as will be explained hereinafter below. In the alternate form of device shown in FIG. 3, there is no monitoring switch 25 having an operating dial 98. The monitoring switch has been replaced bysimplifying the circuit to provide a first jack means 210 having a movable cutoff am 274 which will serve to cut off'the loudspeaker 214 when an earphone plug or other plug is inserted into jack means 210. When it is desired to have the loudspeaker function as well as the earphone or other device to be plugged in, the earphone plug such as a plug 23 is removed from jack means 210 and plugged into jack means 216 which is a simple jack without cutoff means and is wired to the circuit in parallel with speaker 214. Thus, in this form of device the cutoff switch is not necessary and the monitoring is accomplished by placing jack plug 23 in either jack means 210 or 216.
1 also provide an amplifier 220 connected to an amplifier plug 222 by means of a cable 224. The amplifier is connected to one or more speakers 226 and 228. In the form of invention shown in FIG. 3 with the circuit of FIG. 4, when amplifier plug 222 is plugged into jack 216, a voice signal spoken into loudspeaker 214-will be carried by the device through the amplifier and may be heard through speakers 226 and 228 over a large area such as the platform of a symphony orchestra or an auditorium. Where the area is small, one speaker may be used, and where the area is large, the two speakers shown, or more,
- may be used. It is to be understood that the amplifier may be resistor 234 through a junction point 236. Variable resistor 234 is connected by a conductor 238 to a fixed resistor 240 which in turn is connected by conductor 242 to a trimming resistor 244. Trimming resistor 244 is connected by conductor 246 to a junction point 248 which inturn is connected to the emitter of a unijunction transistor 250. Junction point 236 is connected to arm 252 of the variable resistor 234 and also to base portion'B2-of transistor 250 through a conductor 254, a fixed resistor 2'56, and a conductor 258. Base portion B-l of transistor 250 is connected to a junction point 260 by means of conductor 262, and junction point 260 is in turn connected to an arm 264 of a variable resistor 268, and also junction point 260 is connected to a conductor 270 which is connected to jack arm 272. Jack arm 272 is connected to jack arm 274 which in turn is connected tojunction point 276, and junction point 276 is connected to conductor 278which in turn is connected to one side of a loudspeaker 214. The other side of loudspeaker'214'is connected by means of a conductor 282 to a junction point 284, thence by conductor 286 to junction point 288, and thence by conductor-290 to'On-Ol'fswitch 292 which in turn is connected by conductor 294 to the power source orbattery 230. Junction point 288 is also connected by a conductor 296 to variable resistor 268. A capacitor 300 is connected by conductors 302 and 304 between junction points 248 and 288.
l have thus described the circuit olFlG. 4 which produces an audible click in a proper tempo a selected in the loudspeaker 214. 1f a jack plug for an earphone 44, such as jack plug 23, is placed into jack means2-l0,jack arm 274'which is a movable arm will be moved to one side breaking contact with jack element 272 and'thereby cutting out the circuit which energizes the speaker 214.1ackplug 23, however, will be cut into the circuit and earphone 44 will be energized with speaker 2'1'4 cu't out. Jack plug 23 will connect jack arm 272 with jack p'ortion 280 which in turn is connected to junction point 308 which is also connected to junction point 284 by means ofa conductor 310. Jack plug 23 would make this connection because its contact points are in turn connected to the earphone 44 which completes'the circ'uit; while at the same time the loudspeaker is cut out because of the lateral displacement ofarm 274br ea'king contact with arm 272.
In order to provide for the simultaneous operation of the speaker 214 and an earphone 44. l have provided a parallel jack circuit in jack 216. Jack 216 is wired in parallel to speaker 214, and when an earphone plug 23 is inserted, it will not cut out the speaker 214. This wiringih parallel is done by connecting one arm 312tojunction point 276 and the other jack contact 314 to junction point 3 8.
l have now described an alternate form of device as shown in FIGS. 3 and 4 which has all ofthe leatures ofthc device as described in FIGS. 1 and 2 with the exception that the monitor switch is eliminated by providing the double jack arrangement 210 and 216. 1 will now describe-the further advantages of the form of invention'sh'own in FlG.'3 when provided with the circuit of FIG/4.
1 may replace earphone=plug 23 and earphone 44 with an amplifier 220 which may be connected to metronome 200 through jack 210 by means of plug 222. When plug 222 is plugged into jack 210, the'signal of the device will be amplified in amplifier 220 and broadcast through one or more speakers such as speakers 226 'and228. Amplifier 220 is rep'resented'by-the box labeled "Amplifier" in the drawings as any suitableftype of amplifier maybe used. When the amplifier 220 is plugged into the device,-the audible signal or tempo beat will be heard through the s'peakersor speaker. and the orchestra leader or an instructor designated at reference numeral 320 may speak into loudspeaker 214 which now acts as a microphone and his'voice with his instructions will be heard together with the tempo beat. This feature of combining the device with an amplifier 220'may, of course, be used in either form of the device. When it is used with the first form of the device, as'described'in FIG. 1, thernonitor switch must be closed so that the loudspeaker is in the circuit in order for the an 8 ohm speaker 214, and an 8 ohm earphone; a 27 mfd, capacitor 300, a 30K potentiometer for variable resistor 234; a 220 ohm resistor 238, a 4K variable resistor for trimming resistor 244, a 5.1K resistor 256, and a 500 ohm variable resistor for volume control 268. These perametcrs are given as illustrative to show components which will work in the invention and for such illustration only.
When the switch 292 is closed, the capacitor 300 is charged, the current from the battery passing through resistors 234, 240 and 244. When the voltage on capacitor 300 reaches a value equal to the peak-point voltage of the unijunction transistor 250, the unijunction transistor fires. When this happens, the impedance between the unijunction transistors emitter E and base B 1, becomes very low so that the voltage on the capacitor 300 is discharged through the parallel combination-of resistor and the speaker. When the capacitor 300 has discharged sufficiently, the unijunction transistor 2'50 turns off. Now capacitor 300 begins to charge up again, repeating the above cycle.
The discharge of capacitor 300. through the speaker 214, causes the speaker 214 to produce an audible click. The frequency of this clicking is determined by the resistor-capacitor relationship (11: 234, 240 and 300). By adjusting variable resistor 234. this resistor-capacitor relationship is changed which thereby causes a change in the frequency speaker clicks. By attaching a calibrated dial 235 to the variable rcsistor 234, the frequency of the clicks can be read directly from the resistor dial.
in order to maintain a high degree of accuracy, a trimming resistor 244 is placed in series with resistors 234 and 240. This permits a factory adjustment so that variances in the manufacture of components can be compensated for and the dial 235 indicating frequency will be accurate and uniform from unit to unit.
Variable resistor 268 which shunts current from the speaker 214, acts as a volume control. The function of resistor 256 is to keep frequency variations due to changes in ambient temperature to a minimum. The audible clicks produced by the device may be emitted from the speaker 214, or the earphone 44, or both, aswell as through the amplifier 220 circuit, as desired.
THE DEVICE AS AN INSTRUCTIONAL AID FOR TYPEWRITING 1n the usual typewriting instruction system, the student is trained to type at a certain number of words per minute after learning the touch system. and this word per minute rate is increased by practice and testing until the student reaches a desired proficiency. Under the present system, a teacher usually times the students as a group by means of a metronome or other timing device, and at intervals gives the students speed tests by means of a phonograph record. These operations are group operations and are not individual operations.
The invention permits a student to work independently from the group at his own pace. He takes a metronome 200 and places an earphone jack 23 into jack 210 to provide for the operation of the device through earphone 44 with the speaker 214 cut out. Earphone 244, while represented as a single earphone, may be part of an earphone device in which there are two earphones or two earpieces so that both ears of the student can be covered to cut out outside noise or disturbing influence.
in accordance with standard typewriting teaching techniques, five clicks represent five strokes of the keys and space bar of the typewriter to represent a word. Thus, 20'
typed words would be represented by I00 clicks of the metronome. and when the metronome is set for clicks per minute. then a typist following each click with a stroke would be typing at a standard speed of 20 words per minute. The student could then learn the speeds from slow to fast by setting the tempo of the metronome and following the clicks as he or she would type.
As the student progressesfthere are timed tests which the student could administer to himself with the device of the invention by providing the self-timer unit which is adapted to be plugged into the device. Ordinarily the device is started and stopped by means of On-Off switch 292. in order to accommodate the self-timer 202, I have provided a timer jack 208 which is very similar to jack 210 in that it is a cutoffjack. Jack 208 is interposed in the circuit along conductor lines 2320 and 232b and it serves to keep the circuit closed through its arms 320 and 322 and a contact point 324. When selftimer jack plug 204 is placed into jack 208, arm 320 is displaced laterally breaking the circuit and stopping the metronome. The timer 202 may then be activated by pressing ()n" switch 326 which will start the timer for the amount of time set by indicator 328 with reference to dial 330.
The timer 202 is any type of standard timer having an electrical contact type switch in which the switch is open when pointer of indicator 328 is pointed at zero and the switch is closed during the interval of travel of pointer 328 from the desired setting back to zero. The switch is connected through cable 206 to the jack 204. On button 326 keeps the circuit through the timer open until such time as On" button 326 is pressed permitting indicator 328 to travel from the desired setting back to zero. Thus, on a minute timer, the circuit may be closed for any interval of time up to 5 minutes. If it is desired to make a 1 minute test, indicator 328 is set at 1 minute; then starting button 326 is pressed allowing the timer to operate to keep the circuit closed for exactly 1 minute; then when indicator 328 reaches zero, the switching mechanism of timer 202 opens the circuit and stops the metronome.
Thus, astudent may insert the timer plug 204, set the timer for the desired nu mberof minutes, set dial 235 for the desired frequency of beats or clicks, then press the starting button 326 of the timer and have the desired number of beats for the desired time interval to complete the test. By using the device of the invention, an entire typewriting system may be selftaught including testing and learning progressive typewriting speeds.
One of the main features of this device is that it is pocket size. For example, a young lady taking a stenographic course may place the entire metronome. device including earphone in her handbag to carry it home from the classroom for practice at home.
Another feature of the device is that the various components including the interval timer 202, the amplifier 220, and the earphone 44 are interchangeable in selected combinations for a variety of uses.
The interval timer 202 is in the form of a variable interval timer which 'is well known in the art and which may be obtained from the H. A. Rhodes Company ofHartford, Connecticut. Such a timer usually has a mechanically spring wound and operated timing mechanism with 'make and break contacts connected to electrical conductors to close and open a circuit and to function as an On-Off power switch. Thus, such a variable interval timer will have a time interval control which would be equivalent to indicator 328 and would have a time interval starting means such as starting button 326 which would make or close the circuit and start the time interval of the device, and would also have a time interval stop means at the end of the sweep of indicator 328 which would stop the motion of the mechanism and break or open the circuit, thus functioning as an On-Off interval timer power switch means. The conductors of such a device as contained in cable 206 are connected to timerjack plug means 204 which, of course, are adapted to be plugged into the timerjack power switch means 208 for the purpose of opening the power switch in the jack 208 to permit the interval timer power switch means to control the device.
While lhave described my invention in its preferred forms, there are many advantages which may be obtained from a pocket sized, battery powered device having a multitude of uses, and it may take other forms than those shown in the specification without departing from the spirit and scope of the invention, and I, therefore, desire to be protected for all forms.
l. A metronome having amain frame comprising an electronic circuit capable of producing audible sounds at a repetitive rate, which rate can be selectively varied, said electronic circuit comprising loudspeaker means for audibly producing said audible sounds and earphone jack means with loudspeaker cutoff switch means in normally closed position including normally closed timer jack power switch means in the circuit, in combination with an interval timer comprising an interval timer power switch, said interval timer being connected to timerjack plug means adapted to fit into said timer jack power switch means, whereby when said timer jack plug means is connected to said timer jack power switch means. said normally closed power switch in said timer jack power switch means will be opened, with said circuit being adapted to he closed and opened by said interval timer power switch means. a i
2. The metronome as defined in claim I in which the main frame ofthe metronome is pocket size. I
3. The metronome combination as defined in claim l, in which said interval timer is a variable interval timer and includes a time interval control for setting the time of the interval, and a starting means for starting the time interval and a I stop means for stopping the time interval.
4. The metronome as define in claim 3 in which the main frame of the metronome is pocket size.
5. The metronome combination'as defined in claim 1 which includes in further combination an amplifier connected to at least one loudspeaker and connected to an amplifier plug adapted to fit into the jack means ofthe device to amplify said audible signal, whereby when said amplifier plug is fitted into a jack means of the circuit to provide a circuit including the loudspeaker ofthe metronome, a second sound signal directed toward said metronome loudspeaker as an input will be amplified at an amplifier loudspeaker as an output.
6. The metronome as defined in claim 5 in which the main frame ofthe metronome is pocket size.
7. A metronome having a main frame comprising an electronic circuit capable of producing audible sounds at a repetitive rate, which rate can be selectively varied, said electronic circuit comprising loudspeaker means for audibly producing said audible sounds and earphone jack means with loudspeaker cutoff switch means in normally closed position. in combination with earphone means connected to an earphone plug adapted to fit into said earphone jack whereby when said earphone plug is connected to said earphone jack, said loudspeaker cutoff switch will be opened and in which said electronic circuit comprises a separate pair of earphone jacks, in parallel, with only one of said earphone jacks comprising the loudspeaker cutoff switch means including normally closed timer jack power switch means in the circuit, in combination with an interval timer comprisingan interval timer power switch, said interval timer being connected to timer jack plug means adapted to fit into said timer jack power switch means, whereby when said timer jack plug means is connected to said timer jack power switch means, said normally closed power switch in said timer jack power switch means will be opened, with said circuit being adapted to be closed and opened by said interval timer power switch means.
8. The metronome as defined in claim 7 in which the main frame of the metronome is pocket size.
9. The metronome combination as defined in claim 7, in which said interval timer is a variable interval timer and includes a time interval control for setting the time of the interval, and a starting means for starting the time interval and a stop means for stopping the time interval.
10. The metronome as defined in claim 9 in which the main frame ofthe metronome is pocket size.
11. The metronome combination as defined in claim 7 which includes in further combination an amplifier connected to at least one loudspeaker and connected to an amplifier plug adapted to fit into the jack means of the device to amplify said audible signal, whereby when said amplifier plug is fitted into a jack means of the circuit to provide a circuit including the 12. The metronome as define main frame ofthe metronome is p d in claim 11 in which the ocket size.