US3422208A

US3422208A - Electronic latching pedal

Info

Publication number: US3422208A
Application number: US483632A
Authority: US
Inventors: Robert D Barry
Original assignee: Wurlitzer Co
Current assignee: Wurlitzer Co
Priority date: 1965-08-30
Filing date: 1965-08-30
Publication date: 1969-01-14
Anticipated expiration: 1986-01-14
Also published as: DE1497866A1; GB1114500A

Description

Jan. 14, 1969 R. D. BARRY ELECTRONIC LATCHING PEDAL Sheet of' 3 Filed" Aug; ISO, 1965 f bmf en@ FWS fr? E Jan. 14, 1969 R. :1B/mm 3,422,208

ELECTRONIC LATCHING PEDAL l Filed Aug. 30, 1965 Sheet 2 01u/DER arr.

olv/DER 115 ggg; 63W @a A Y .Y a:

Jan. 14, 1969 R. D. BARRY ELECTRONIC LATCHING PEDAL Sheet Filed Aug. 50, 1965 Y W w% www RR H l; \W llllllllllllllllllll Il. ,ul Mk1 QQNN WNW United States Patent O 18 Claims ABSTRACT F THE DISCLOSURE A monophonic organ pedal switching circuit wherein each note is switched through a diode which is normally on. A plurality of neon bulbs, one for each note, is included. When any pedal switch is closed by depression of the pedal, positive voltage is applied to the corresponding neon bulb, causing it to re, and biasing the corresponding diode for conduction. Simultaneously, a negative pulse is applied to all other neon bulbs to insure that any bulb which remains in firing condition is cut oli. Upon release of a pedal and opening of the corresponding switch, a lesser voltage remains applied to all of the neon bulbs which is sufficient to maintain in firing condition the one bulb that has most recently been red, but which is not suflicient to tire or ignite any other neon bulb, whereby the last note played can be sustained.

This invention relates to the art of electronic musical instruments, and more specifically to an electronic latching pedal or circuit for playing pedal tones as in an electronic organ with sustain, and with cancellation of a sustaining note when a subsequent note is played.

As is known, it is desired to have the pedal tones on an electronic organ sustain, i.e., a note should not decay abruptly as soon as the corresponding pedal is released. On the other hand, it generally is not desirable to have one note to continue to sustain when a subsequent note is played. Various electro-mechanical switching expedients have been utilized heretofore to provide for sustain and cancellation thereof. Electr-o-mechanical devices inherently present certain types of service problems, and also inherently are a source of noise. v

Accordingly, it is an object of this invention to provide a completely electronic system for accomplishing the same pur-poses.

In particular, it is an object of this invention to provide an electronic switching circuit utilizing electronic switches for playing the pedal notes of an electronc organ, -for sustaining a note that has been played, and for canceling a previously sustaining note when another note is played.

Yet another object of the present invention is to provide a switching system as heretofore set forth using a single gate and sustain capacitor for each pedal footage stop.

Specifically, it is an object of this invention to utilize neon bulbs for switching potentials to control the conduction of switching diodes in an electronic organ pedal switching circuit.

A further specific object of the present invention is to provide a common voltage supply means operative with a plurality of voltage switching neon bulbs so arranged that one neon bulb is extinguished as a subsequent one fires.

Other and further objects and advantages of the present invention will be apparent from the following description when taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of an electronic organ 3,422,208 Patented Jan. 14, 1969 constructed in accordance with the principles of the present invention;

FIG. 2 is a schematic wiring diagram of a basic circuit exemplifying the pedal switches and accompanying electronic switches for eiiecting playing of selected pedal notes;

FIG. 3 is a schematic wiring diagram of an electronic organ pedal note divider circuit and gating circuit for effecting sustain;

FIG. 4 is a similar circuit useful with a different type of waveform input; and

FIG. 5 is a schematic wiring diagram of a portion of a commercial electronic organ as built in accordance with the principles of the present invention.

Referring now in greater particularity to the drawings, and irst to FIG. 1, there will be seen an electronic organ 10 comprising a case 12 having a pair of manuals or

keyboards

14 and 16, generally in accordance with conventional practice. Various stop tablets 18 are provided for effecting switching functions, most of which are not directly involved in the present invention. The organ case is provided with a music rack 20, with a grill 22 behind which loud-speakers are mounted, and with a swell pedal 24 for controlling the overall volume. In addition, the organ is provided with a pedal clavier comprising a plurality of pedals 26 for playing the pedal notes of the organ.

Turning now to FIG. 2, along the right side thereof will be seen a plurality of tone .generators 28. The tone generators 28 may be of any suitable or known type, or for purposes of the present invention preferably provide a square wave output. The number of generators is equal to the number of pedal notes, i.e., an octave plus one of semi-tones o-r a total of 13. Only three are shown, and additional parts are suggested by dashed lines, the cir'- cuits being duplicated and unnecessary of specific disclosure. Each generator is connected to a resistor 30, and this resistor leads to a junction 32. The junction is connected through a diode 34 poled for conduction of positive current from left to right to a collector bus 36 grounded through a shunt resistor 39, and connected through a series coupling capacitor 40 to dividers 42, and hence to an amplifier 44 and loudspeaker 46. As is common in electronic organ practice, the generators 28 actually generate notes higher than the desired pedal tones, and these are divided once in frequency for the eight foot stop, and twice for the sixteen foot stop.

Normally the diodes 34 do not conduct signals from the generators to the collector bus 36. Switching circuits are provided for individually biasing the diodes 34 for conduction, and these circuits will now be set forth.

To each junction there is connected a series resistor 48, and this in turn is connected to a junction 50. A capacitor 52 of rather large size is connected in parallel with a resistor 54, having at the top end a junction 56 connected directly to the junction 50; the resistor-capacitor parallel combination being grounded as shown. The junction 56 is' connected to a neon bulb 58, and each neon bulb is connected to a junction 60. Each of the junctions 60 is connected through a resistor 62 to a common bus 64.

The bus 64 is connected by a line 66 to a junction 68 on a voltage divider 70 comprising a resistor 72 connected at a junction 74 to a resistor 76, the latter being connected at the junction 68 to a grounded resistor 78. The top end of the resistor 72 is connected to a positive 180 volts direct current source, as indicated, and is also connected to a resistor 80. The resistor is connected to a junction 82, and this resistor is connected to a capacitor 84 leading to the junction 74. The junction 82 is connected to a movable contact 86 of a switch 88.

The switch 88 comprises a pedal switch operated by one of the pedals 26, and has an additional movable contact 90 ganged as indicated at 92 with the contact 86. The contact 86 normally engages Va fixed contact 94, and each fixed contact 94 is connected by means of a wire to the next adjacent (above) movable switch contact 86. The movable contact 86 is arranged to leave the fixed contact 94 and to move into engagement with a fixed contact 98 when a pedal corresponding thereto is depressed. Each fixed contact 98 is connected by a wire 100 with the corresponding junction 60.

Each movable switch contact 90 is connected to a supply line or bus 102 maintained at -180 volts D.C. Each contact 90 normally is not in engagement with a fixed contact, but upon depression of a corresponding pedal 26 a contact 90 moves into engagement with a corresponding fixed contact 104. All of the fixed contacts 104 are connected to a collector bus 106 which leads to the amplifier 44 and which has ashunting sustain capacitor 108.

When the organ is first turned on, none of the neons 58 is ignited. Closure of one of the key switches 88, and specifically engagement of a movable contact 86 with a fixed contact 98, for example the bottom one in FIG. 2, will raise the potential of the neon 58 in series with the switch and cause ignition thereof. Junction 82, which previously has been substantially at the supply source voltage of +180 volts will drop in voltage to approximately 90 volts. Surge current through the capacitor 84 momentarily drops junction 74 to approximately 90 volts, and this in turn drops the voltage at junction 68.

Current drawn through the neon bulb 58 to the resistor 54 causes a voltage drop across the resistor 54, and this in turn forward biases the corresponding diode 34. The signal supplied by the corresponding generator 28 thus is carried through the now conducting diode 34, and through capacitor 40 to the dividers 42 and on to the amplifier 44.

At the same time, movable contact 90 was moved into engagement with fixed contact 104, thus supplying -180 volts D C. from the supply line 102 to the collector 106 and on to the amplifier 44, turning on a gate in the amplifier to conduct the signal from the dividers 42. If the lower switch 88 is now released, potential is held on the line 106 for a predetermined time by the capacitor 108, whereby to provide sustain.

If another of the switches 88, for example, the second from the bottom, is now operated by its corresponding pedal while the sustained note is still sounding, the corresponding neon bulb 58 (second from the bottom in the present example) is ignited. Surge current through the capacitor 84 drops junction 82 to about 90 volts, thus dropping junction 68 below the potential necessary to maintain the lowermost neon bulb 58 firing. Thus, one neon is extinguished as another ignites. The junction point 68 again rises to its approximate 100 Volts D.C. potential, which is sufiicient to maintain ignition of the last ignited neon bulb, even though the newly closed switch be allowed to open by release of the corresponding foot pedal.

It will be observed that potential is supplied to the movable switch contacts 86 in series from the positive 180 volt source, and if any two switches are operated at the same time, only the lowermost will have any effect on its corresponding neon bulb, since the series chain will be broken before reaching the upper of the two switches. Thus, the present switching system also comprises a preference network, which may be considered to be a low note perference with the lowest switch and associate parts corresponding to the lowest pedal note, etc.

In the invention as heretofore shown and described, sequencing of the switch contacts and 86 and 90 is important. The switch contact 86 must make contact with its adjacent fixed contact 98 at least as soon as, and preferably slightly before the movable switch contact engages its fixed contact 104 to insure that a new note will be playing before its readout is initiated. In order to eliminate the second movable switch contact, and to insure proper sequence, a variation in the output circuit is employed, as shown in FIG. 3. The switching circuit of FIG. 2 may be employed in connection with FIG. 3 without change, except for elimination of the 180 volt D.C. supply line, the second movable switch contact 90, and the connecting line 106 leading to the amplifier. Thus, the diodes 34 (of which only nine are illustrated), the collector 36, the resistor 38 and capacitor 40 are as heretofore shown and described. The capacitor 40 is connected to the dividers 42, specifically illustrated as an eight foot divider 110 connected to a junction 112, the junction 112 being connected to a sixteen foot divider 114. The junction 112 is connected to a diode 116 poled to conduct positive current from left to right. The diode 116 is connected to a junction 118, and from there through a capacitor 120 to the amplifier 44 and loudspeaker 46.

The 16 foot divider 114 is connected to a similarly poled diode 122, the latter being connected to a junction 124, and from the junction to a capacitor 126. The capacitor is connected to the amplifier 44.

From the collector bus 36, connection is made through a resistor 128 to an input junction 130 through a twostage transistor switching circuit 132 comprising a first transistor 134 having the base 136 thereof connected direct to the junction 130. The transistor 134 is of the p-n-p type, and the collector 138 thereof is connected through a resistor 140 to a supply line 142 of 20 volts D.C. The base also is connected through a resistor 144 to the supply line 142. The emitter 146 is connected to a junction 148 leading through a resistor 150 to a source of positive potential indicated at |30 volts.

The collector 138 also is connected directly at 152 to the 'base 154 of another p-n-p transistor 156, the collector 158 of which is directly connected to the negative supply line 142. The emitter 160 is grounded through a resistor 162. The junction 148 also is grounded through a resistor 164.

The emitter 160 also is connected to a diode 166, poled to conduct positive current toward the emitter from right to left as shown in the drawing. The opposite side of the diode 166 is connected to a resistor 168 leading to a sustain switch 170, grounded on the other side, and the diode is also connected to a resistor 172 leading to a junction 174. The junction 174 is grounded through a capacitor 176, and further is connected to a junction 180 which leads through respective resistors 182 and 184 to the junctions 124 and 118.

Normally the transistor 134 conducts quite heavily, and this in turn biases the transistor 156 off. Whenever one of the key switches (previously described movable contact 86, etc.) is operated, the voltage on the collector line 36 rises from a normal quiescent potential of approximately one volt to about four or five volts, thus cutting off transistor 134. The collector voltage of transistor 134 thus approaches the supply voltage of -20 volts, and this in turn turns on transistor 156, allowing nearly 2'0 volts negative to appear on the collector 160 of this transistor. This charges capacitor 176 through diode 166 and resistor 172. The negative potential on capacitor 176 is applied to resistors 182 and 184 to turn on the

diodes

122 and 116, and thus to conduct the eight and sixteen foot -dividers respectively t0 the amplifier 44. When a pedal is released, the capacitor 176 discharges only very slowly, thereby causing the note to sustain. If it is desired not to have any substantial sustain, then the switch is closed. The capacitor 176 thereupon discharges through 4the resistor 168 quite rapidly in series with the resistor 172.

The circuits as noted heretofore are intended for use primarily with tone generators providing a square wave output. This is a desirable output in that it is rich in harmonics. However, there m-ay be times in which it is desired to operate with a sine wave generator, and a suitable circuit is shown in FIG. 4. Many of the parts in the circuit are similar to those heretofore shown and described in connection with FIG. 2, and similar numerals therefore are utilized to identify similar parts with the addition of the suix a. Thus, the voltage divider 70a is generally the same as heretofore shown and described. However, voltage regulation is supplied by means of an input resistor 186 connecte-d from the positive 180 volt D.C. supply to the top of the voltage divider, the junction between the top of the voltage divider and the input resistor being grounded through a shunt combination of three series-connected

neon bulbs

188, 190 and 192, the latter being paralleled by a resistor 194.

The tap or junction 68a -on the voltage divider is again connected by a line 66a and a further line 64a and resistors 62a to the neons 58a for holding a fired neon in the firing or ignited condition.

Keying potential to fire a neon, the neons normally being off at the start of playing, is supplied from the junction 82a to the movable contacts 86a of the various key switches 88a, only three thereof being shown. The -fixed contacts 98a of the key switches, in this case single pole, single throw switches, are connected by wires 10011 to the neons 58a.

At the output side of the neons there is a significant distinction. The neons are again connected to series resistors 48a, but are shunted to ground by diodes 196, each being poled to conduct positive current to ground. The generators 28a are coupled by means of capacitors 198 to the junctions between the resistors 98a and the output diodes 34a.

In addition to the foregoing, a wire 200 leads from the junction 82a (labeled at two different points in FIG. 4 for convenience) to a pair of series connected neons 20-2 and 204 leading to a resistor 206. The resistor 206 is connected to the base 208 of an n-p-n transistor 210, the emitter 212 of which is grounded through a resistor 214. Positive potential of +105 volts D.C. is connected through a resistor 216 to the collector 218 of the transistor, and the output is taken from the collector 218 through a diode 220 poled to conduct positive current from left to right and leading on to the gate in the output amplifier.

Normally, the keying circuit transistor 210 is biased through the

neon bulbs

202 and 204 into heavy conduction during standby periods. The collector 218 therefore is at a very low voltage, and little or no voltage is transmitted through the diode 220. However, when a key switch 88a is closed, the potential at junction 82a drops to 70 to 80 volts. This is too low a potential to maintain the series connected neon bulbs 20-2 and 204 in firing condition and these two bulbs therefore extinguish. The bias then changes such that the transistor 210 stops conducting, whereby substantially +105 volts is applied to the diode 220, and this supplies the necessary positive potential to the gate in the amplifier to cause a tone to be transmitted.

As to the keying circuit, when no key switch y88a is closed, each capacitor 198 charges to the peak negative A.C. signal potential, since there is no D.C. return path or load on the rectifier circuit comprising the

capacitor

198 and 34a. Thus, no output A.C. signal voltage is available to the amplifier.

Upon closing of a key switch, for example, the bottom most of the switches 88a, potential is applied from the point 82a to the adjacent neon 58a. This causes the neon 58a to fire, and also causes the diode 196 to conduct. This provides a D.C. return path for the rectifier circuit comprising the capacitor 198 and diode 34a, whereby positive pulses are passed by the capacitor 40a to the amplifier, or strictly speaking, to the divider circuits, then on to the amplifier.

When the pedal is released so that the switch 88a opens, the bulb 58a remains conducting by virtue of connection of the wires 66a to the junction 68a at about +100 volts. However, subsequent closure of another key switch drops the potential at 82a, providing a negative pulse across the capacitor 84a which drops the potential applied to the previously fired neon bulb 58a to cause it to extinguish. This removes the D.C. return path from the rectifier circuit of the previously played note, and the previously played note is cut olf.

A practical circuit embodying the principles of the present invention as actually utilized in a commercial electronic organ is shown in FIG. 5. Certain of the parts that are shown therein are similar to those heretofore shown and described, and are identified by similar numerals with the addition of the suix b. Thus, tone generators 28b are shown, coupled through capacitors 198b to a junction between resistors 48h and diodes 34h, normally biased 01T. The diodes are connected to a common collector line 36b to the junction between a shunting resistor 38b and a capacitor 40b leading to the dividers 42b through means including a wire 222.

Each resistor 48b is connected at the top end to a shunting diode 196b, normally biased off, and to a neon bulb 58b. The neon bulb at the top end is connected to the fixed contact 98h of a pedal switch 88b, the movable contact 8'6b of which is connected to a positive bus 224. This bus is connected through a resistor b to a supply line 226 receiving a positive 180 volts D.C. at a plug connector 229. The supply line 226 also is connected through a resistor 228 to a bias line 230, and a capacitor 84b is connecte-d between the

lines

224 and 230.

It will be understood from what has gone before that the full complement of key switches 88b and associated parts is provided, there being a total o-f 13 switches and associated individual circuits for the organ under consideration which has 13 pedal notes, one octave of semitones plus one.

A holding circuit for the respective neons 58h is provided by means of a diode 231 and a paralleling resistor 233 connected from the line 230 to each neon I58b.

Connection is made from the line 224 to series connected neon bulbs 202b and 204b, a high value biasing resistor 232 being connected to ground from between the two neon bulbs. The neon bulb 204b is connected through a resistor 206]; to the base of transistor 210b. Connection also is made from the resistor 206b through another resistor 234 to the emitter of the transistor 208b, the latter being grounded through a resistor 21411. The emitter also receives a -1 volt D.C. bias through line 236 leading to the plug 229.

The collector is connected through resistor 216b to positive supply line 238 shunted to ground by capacitor 240, and connected through resistor 242 to a source of +20 volts D.C. supplied through the plug 229.

A further connection is made from the collector of the transistor 208b through a resistor 242 to the base of an n-p-n transistor 244 having the emitter thereof grounded through a resistor 246. The collector is connected through Va Wire 248 to a cymbal switch of a rhythm accompaniment unit forming no particular part of the present invention, but fully shown and described in the accompanying application of Harold O. Schwartz and Peter E. Maher, (Transistorized) Electronic Percussion Unit with Organ, Ser. No. 448,362, filed Apr. l5, 1965.

Connection further is made from the collector of' the transistor 208b to the vbase of the transistor 250. Like the remaining transistors in the circuit of FIG. 5, this is n-p-n transistor. The collector is connected direct to the line 238, while the emitter is grounded through resistor 252. Connection is made from the emitter through a capacitor 254 .and a shunting resistor 256 to a wire 258 leading to a diode 260 which goes to a drum switch for the rhythm accompaniment device previously referred to in the Schwartz et al. application.

Connection further is made from the emitter of the transistor 250 through diode 1681;, paralleled by a resistor 262 to a line 264 leading through resistor 172b to gating line 178b.

A two pole double throw sustain switch 170b has a movable contact thereof grounded, and is engageable with a fixed contact 266 which is connected to the line 264 through a relatively low value resistor 267 or with a fixed contact 268 which is connected through a relatively high value resistor 168b with the wire 264. The movable contact also can be left in a center position away from both fixed contacts.

With the switch 170b in the center or open position as shown sustain is on at a maximum. With the contact closed against the fixed contact 266, there is little sustain, and with the movable switch contact closed against the fixed contact 260b, there is a short sustain.

The sustain line or gating line 178b leads across a shunting sustain capacitor 176b to the junction 180b between resistors 182b and 184b.

The output line 222 from the pedal switches leads to the base of a transistor 270, the base being connected to ground through a resistor 272. The emitter also is grounded through a resistor 274, while the collector is conected through a resistor 276 to a +16 volt D.C. bus 278 receiving its potential supply from a remote source by way of the plug 229. The collector of the transistor 270 is coupled through a capacitor 280 to an eight foot divider 110b. This divider comprises a pair of transistors and suitable interconnecting resistors and capacitors to form an Eccles-Jordan circuit having an output on line 282 one-half the input frequency. The divider 110b is coupled by a capacitor 384 to the 16-foot divider 114b, also comprising a transistorized Eccles-Jordan circuit having an output line 286 providing oscillations at one-half the frequency of the first divider 110b.

Operation of the amplifying transistor 270 is such that the input signal is amplified to the point of clipping, and thereby to limit to a consistent peak. The output of the two Eccles-Jordan divider circuits common namely 11012 and 114b, is in each case a square wave. The circuits are sufiiciently well-known that no particular detailed description is believed warranted.

The eight-foot divider output line 282 is connected to a diode 116b poled, as shown, to conduct a positive current from right to left, and the right side of the diode is connected to the junction 118b with the resistor 184b, and on through coupling capacitor 12012 and series resistor 288 to the amplifier, including the filter circuits. A capacitor 290 shunts the junction 118b to ground.

Similarly, the output line 286 of the sixteen foot divider 114b is connected to a diode 122b leading to the junction 124b with the resistor 182. This junction is shunted to ground by a resistor 294, and is connected through coupling capacitor 126b and series resistor 296 on to the amplifier, including the filter circuits.

Operation of these circuits is similar to that of the circuits heretofore shown and described. Considering first one of the key switches 88b and associated parts, when the organ is first turned on the potential on the line 230 acts through one of the diodes 231 to turn on a neon bulb 58b. This is at random, and it is the neon bulb 58b with the lowest tiring potential that normally comes on. Current through the resistor 228 drops the potential on line 230 sufficiently low that no other neons 58b are ignited after the first one. There is no output since the signal is blocked at diodes 116b and 122b.

It will be appreciated that the leakage across any pedal switch `88h could be on the order of magnitude of 5-10 megohms whereby a corresponding neon bulb 58b might accidentally be fired. This is prevented by resistor 233 which acts as a voltage divider with the switch leakage resistance. A diode 231 allows a holding voltage of about 65-70 volts to be applied to the previously ignited neon bulb 58-b to maintain it ignited, while still providing isolation from line 230 to line 224. As in the embodiment of FIG. 4, when a neon bulb 58h is not conducting, there is no return path for the rectifier comprising capacitor 198b and diode 98a. Hence, the capacitor 198b simply charges up, and no signal is carried. However, when a switch 88b is closed, approximately 150 volts positive potential is applied from the line 224 to the corresponding neon 58h thereby to fire it and to render the diode 196b conductive. A return path is provided and the diode 34b conducts to provide output signals on the line 36b, and subsequently on the line 222.

When any subsequent key switch 82b is closed, the potential on the line 224 drops, applying a pulse through capacitor 84h and extinguishing previously ignited neon 58h.

The neons 202b and 204b come on when the organist turns on and biases the transistor 20817 for heavy conduction, and this holds transistor 250 off. When a key switch is closed, the current drawn through the resistor `8b causes the potential on the line 224 to drop to a point where the two neons 202b, 204b cannot remain ignited in series. Upon this occurring, the transistor 208b turns off, and the transistor 250 turns on. Output potential through the diode 166b thereby is applied through the line 178b to turn on the diodes 116b and 122b and thereby to allow the divided signal from the eight and six foot dividers b and 114b to go through the output circuits to the amplifier.

Although those skilled in the art will have no difficulty in choosing proper circuit values, the following are set forth by way of example:

C198-.0047 mfd. C240-100 mfd. C2S4-2 mfd. C280-.0056 mfd. C290-.015 mfd. C294-.047 mfd. R30-100K ohms R38--22K ohms R38b-100K ohms R48b-10K ohms R48b-22K ohms RS4- 10K ohms R62-47K ohms R72-22K ohms R72a--33K ohms R76-68K ohms R76a-56K ohms R78--130K ohms R78a--120K ohms RSO- K ohms R80a-33K ohms R128--39K ohms R140-12K ohms R144-390K ohms RISO- 8.2K ohms 11162-680 ohms R164-470 ohms RMS-4.7K ohms R172--l470 ohms R172b-1K ohms R-100K ohms R180b-270K ohms R182--l00K ohms R182b--56K ohms R184-l00K ohms R184b56K ohms R186-27K ohms R194470K ohms R206-390K ohms R206b-1 mohms R214-470 ohms R216-22K ohms R228-270K ohms R232-10 mohms R233-1.5 mohms R234-47K ohms R242-100K ohms R246-68 ohms R252-15K ohms R256-4.7K ohms R262-220K ohms R272-1OK ohms R274-100 ohms R276-l0K ohms R288-27K ohms R296-27K ohms The invention is claimed yas follows:

1. A switching circuit for an electronic musical instrument comprising a plurality of signal input means, signal output means, voltage supply means providing a first voltage sufficient to fire a gas tube and a second volt-age sufficient to maintain a gas tube in firing condition but not sufficient to start firing thereof, a plurality of like means respectively interconnetcing said plurality of signal input means Iand said signal output means, each of said connecting means including a normally non-conducting electronic switch in series between a signal input means and said signal output means and a normally nonconducting gas tube connected to a respective electronic switch, means including a plurality of key switch means interconnecting said voltage supply meansfirst voltage and said gas tubes for selectively firing said gas tubes, a gas tube when firing rendering a corresponding electronic switch conductive to convey Ia singal from a respective signal input means to said signal output means, means interconnecting said voltage supply means second voltage with said gas tubes to maintain a firing tube in firing condition, and means interconnecting said key switch means and said voltage supply source second voltage to lower said second voltage upon operation of a subsequent key switch to extinguish a previously fired gas tube.

2. A switching circuit for an electronic musical instrument comprisin-g a plurality of signal input means, signal output means, voltage 4supply means providing a first voltage sufiicient to fire a gas tube and a second voltage sufficient to maintain a gas tube in firing condition but not sufficient to start firing thereof, a plurality of like means respectively interconnecting lsaid plurality of signal input means and said signal output means, each of said connecting means including a normally non-conducting diode in series bet-Ween a signal input means and said signal output means and a normally non-conducting gas tube connected to a respective diode, means including a plurality of key switch means interconnecting said voltage supply means first voltage and said gas tubes for selectively firing said gas tubes, a gas tube when firing rendering a corresponding diode conductive to convey a si-gnal from a respective signal input means to said signal output means, means interconnecting said voltage supply means second voltage with said gas tubes to maintain a firing tube in ring condition, and means interconnecting said key switch means and said voltage supply source second voltage to lower said second voltage upon operation of a subsequent key switch to extinguish a previously fired gas tube.

3. A switching circuit as set forth in claim 2 wherein said voltage supply means comprises a potential source and a voltage divider, said first and second voltages being taken at different points on said divider.

4. A switching circuit as set forth in claim 3 wherein the means for lowering said second voltage is effective only momentarily to lower said second voltage.

5. A switching circuit for an electronic musical instrument comprising a plurality of signal input means, signal output means, voltage supply means providing a first voltage suliicient to fire a gas tube and a second voltage suliicient to maintain a gas tube in firing condition but not sufficient-to start firing thereof, a plurality of like means respectively interconnecting said plurality of signal input means and said signal output means, each of said connecting means including ya normally non-conducting diode in series between a signal input means and said signal output means and a normally non-conducting gas tube connected to a respective diode, means including a plurality of key switch means interconnecting said voltage supply means first voltage and said gas tubes for selectively firing said gas tubes, a gas tube lwhen firing rendering a corresponding diode conductive to convey a signal from a respective signal input means to said signal output means, means interconnecting said voltage supply means second voltage with said -gas tubes to maintain a firing tube in firing condition, means interconnecting said key switch means and said voltage supply source second voltage to lower said second voltage upon operation of a subsequent key switch to extinguish a previously fired gas tube, said signal output means including normally closed electronic gate means, and means interconnecting said key switch means and said normally closed electronic gate means for opening said gate means upon closure of a key switch means.

6. A switching circuit as set forth in claim 5 wherein the means interconnecting the gate means and the key switch means comprises an additional set of contacts on each key switch means.

7. A switching circuit as set forth in claim 5 wherein the means interconnecting the Igate means and the key switch means comprises gas tube means normally conducting to bias said gate means off, and means interconnecting said key switch means and said gas tube means for extinguishing said g-as tube means upon closure of any of said key switch means.

`8. A switching circuit for an electronic musical instrument comprising a plurality of signal input means, signal output means, voltage supply means comprising a,voltage supply means having a first voltage output sufficient 'to fire -a gas tube and a second voltage output sufficient to maintain a gas tube in firing condition but not suicient to start firing thereof, a plurality of like means respectively interconnecting said plurality of signal input means and said signal output means, each of said connecting means including a normally non-conducting electronic switch in series 'between a signal input means and ksaid signal output means and a normally non-conducting. gas tube connected to a respective electronic switch, means including a common resistor and a plurality of key switch means interconnecting said voltage supply means first voltage output and said gas tubes for selectively firing said gas tubes upon closure of a respective key switch means, a gas tube when firing rendering a corresponding electronic switch conductive to convey a signal from a signal input means to said signal output means, means interconnecting said voltage supply means second voltage output with said gas tubes to maintain a firing tube in firing condition, and a capacitor connected from said common resistor to said second voltage output on said volta-ge supply means for momentarily dropping said second voltage upon operation of a subsequent key switch to extinguish a previously fired gas tube.

9. A switching circuit for an electronic musical instrument comprising a plurality of signal input means, signal output means, volt-age supply means comprising a voltage divider having a first voltage output sufficient to fire a gas tube and a second voltage output sufficient to maintain a gas tube in firing condition but not sufiicient to start firing thereof, a plurality of like means respectively interconnecting said plurality of signal input means and said signal output means, each of said connecting means including a normally non-conducting electronic switch in series between a singal input means and said signal output means and a normally non-conducting gas tube connected to a respective electronic switch, means including a common resistor and a plurality of key switch means interconnecting said voltage divider first voltage output and said gas tubes for selectively firing said gas tubes upon closure of a respective key switch means, a gas tube when firing rendering a corresponding electronic switch conductive to convey a signal from a signal input means to said signal output means, means interconnecting said voltage divider second voltage output with said gas tubes to maintain a firing tube in firing condition, and a capacitor connected from said common resistor to said second voltage output on said voltage divider for momentarily dropping said second voltage upon operation of a subsequent key switch to extinguish a previously fired gas tube.

10. A switching circuit as set forth in claim 9 wherein said signal output means comprises a normally closed electronic gate, and means interconnecting said gate and said key switch means for opening said gate upon closure of any of said key switch means.

11. A switching circuit as set forth in claim 10 wherein the means interconnecting said gate and said key switch means includes a second set of contacts on each of said key switch means.

12. A switching circuit as set forth in claim 9 wherein the means interconnecting said electronic gate and said 11 key switch means comprises gas tube means biased through said common resistor to ring condition and biasing said gate oli, the voltage supplied through said first resistor to said gas tube means dropping upon closure of any key switch means to extinguish said gas tube means for biasing said electronic gate on.

13. A switching circuit for an electronic musical instrument comprising a plurality of signal input means, signal output means, a plurality of like means respectively interconnecting said plurality of said signal input means and said signal output means, each of said interconnecting means including a normally non-conducting electronic switch in series between a signal input means and said `signal output means and a normally non-conducting gas tube connected to a respective electronic switch, a plur-ality of key switch means each comprising a tirst set of means, means including said first set of contacts connecting said voltage supply means and said gas tubes respectively for selectively firing said gas tubes, a gas tube when tiring rendering a corresponding electronic switch conductive to convey a signal from a signal input means to said signal output means, means interconnecting said voltage supply means and said gas tubes for supplying to said gas tubes a voltage suicient to maintain firing but not suicient to start firing thereof, means interconnecting said voltage supply means and said last mentioned connecting means -for lowering the potential supplied to said gas tubes to extinguish any previously fired tube upon closure of a corresponding set of first contacts, said signal output means including a normally closed electronic gate, an additional voltage source, and means including said second contacts interconnecting -said -additional voltage source and said electronic gate for opening said gate upon closure of any of said second contacts.

14. A switching circuit for an electronic musical instrument comprising a plurality of signal input means, signal output means, means including a plurality of key switch means interconnecting `said signal input means and said signal output means and selectively operable to connect a respective signal input means to said signal output means, said signal output means including normally closed electronic gate means, voltage supply means, means for controlling the operation of said electronic gate means and interconnected therewith and comprising gas tube means, means interconnecting said voltage supply and said gas tube means for normally maintaining said gas tube means in a first condition of conductionor nonconduction, means interconnecting said voltage supply, said key switch means and said gas tube means and operative upon closure of a key switch means to reverse the condition of conduction or non-conduction of said gas tube means and thus to bias said electronic gate open, and a normally conducting transistor interconnecting said gas tube means and said electronic gate to bias said gate closed, said transistor being cut oi and biasing said g-ate open when the condition of conduction of said gas tube means reverses.

15. A switching circuit as set forth in claim 1S and 4further including a diode interconnecting said transistor and said electronic gate, said diode being normally cut off by conduction of said transistor and being biased for conduction upon stopping of conduction of said transistor and thereupon biasing said electronic gate for conduction.

16. A switching circuit for an electronic musical instrument comprising a plurality of signal input means, signal output means, a plurality of like means respectively interconnecting said plurality of signal input means and said signal output means, each of said interconnecting means including a rectifier circuit normally having a return path including a normally non-conducting electrically controlled circuit element and hence effective to block signal transmission from said signal input means to said signal output means, and means including a plurality of key switch means respectively connected to said rectier means and to said circuit element and a potential means to render said circuit element conductive upon operation of said key switch means and thereby providing a return path for said rectifier means to render said rectifier means effective to transmit a signal from a respective signal input means to said signal output means.

17. A switching circuit as set forth in claim 16 wherein each rectifier means comprises a capacitor connected to the respective signal input means and a series connected diode, and wherein the means for providing a return path further includes a shunt diode connected from a position between said capacitor and said series connected diode to ground and normally non-conducting, said shunt diode being rendered conductive upon operation of a corresponding key switch to provide a return path.

18. A switching circuit for an electronic musical instrument comprising a plurality of signal input means, signal output means, voltage supply means providing a first voltage sufficient to fire a gas tube and a second voltage sufficient to maintain a gas tube in lfiring condition but not suicient to start tiring thereof, a plurality of like means respectively interconnecting said plurality of signal input means and said signal output means, each of Isaid 4connecting .means including a normally non-conducting diode in series between a signal input means and said signal output means and a normally non-conducting gas tube connected to a respective diode, means including a plurality of key switch means interconnecting said voltage supply means first voltage and said gas tubes for selectively firing said gas tubes, la gas tube when firing` rendering a corresponding diode conductive to convey a signal from a respective signal input means to said signal output means, means interconnecting said voltage supply means second voltage with said gas tubes to maintain a firing tube in firing condition, means interconnecting said key switch means and said voltage supply source second Voltage to lower said second voltage upon operation of a subsequent key switch to extinguish a previously fired gas tube, said series input means including a capacitor connected in series with said diode, and a second diode connected from the previously mentioned diode and adjacent gas tube to ground, said second diode being normally nonconductive and rendered conductive upon firing of a corresponding gas tube to provide a D.C. return circuit for the rectifier comprising said capacitor and said first mentioned diode.

References Cited UNITED STATES PATENTS 3,227,799 1/1966 Holman et al 84-l.26

ARTHUR GAUSS, Primary Examiner.

B. P. DAVIS, Assistant Examiner.

U.S. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,422,208 January 14, 1969 Robert D. Barry It is certified that error appears in the above identified patent and that said Letters Patent are hereby Corrected as shown below:

Column 2, line 4l, "39" should read 38 Column ll, lines 16 and "set" insert contacts and a second set of contacts, voltage supply line 59, claim reference numeral "l5" should re Signed and sealed this 17th day of March 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, J r.

Commissioner of Patents Attesting Officer