US2482184A - Chronographic apparatus and method - Google Patents

Description

H. w. HOFFMAN ETAL CHRONOGRAPHIC APPARATUS AND METHOD sept, 2o, 194,9.

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w. HOFFMAN STAI. 2,482,184 CHRONOGRAPHIC APBARATUSAND METHOD Sept.v zo, 1949.-

Filed may 26,f 1945 f @Rove H. HELMER.

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Sept.20, 1949. H. w. HOFFMANl ETAL 2,482,184

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CHRONOGRAPHIC APPARATUS AND METHOD 8 Sheets-Sheet 7' Filed lay 26, 1945 Sept. 20, 1949. H. w. HOFFMAN ErAl. v 2,4825184 CHROOGRAPHIC APPARATUS AND METHOD Findlay 26, 1945 a sheets-snm a FES." 15 Figf 16 Ramal: Dsuncron INVENTORSI HARRY \l-/. HOFFMAN. @ROVER H. HELMER.

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Patented Sept. 2o, 1949 CHRONDGBAPHIC generos AND METH() William Henman, Anoka, and Grover H..-

Helmer, St. Louis Park, Minna,

assignora to Federal Cartridge Corporation, Minneapolis, Minn., a corporation of Minnesota y appuesaoamy ze, 1945, sesame. secon s cum. (ci. isi-15) This invention relates to improved chronosraphic apparatus and methods and more particularly to apparatus and methods for timing events at exceedingly short intervals. The apparatus and methods of the invention are of. narticular usefulness in measuring and recording the performance of ordnance projectiles and isV hereinafter speciilcally described with reference to such work, although it must be understood that such speciilc application is merely illustrative.

It is an object oi the invention to provide improved chronographic apparatus and methods and particularly to provide apparatus and methods for accurately indicating and recording time intervals of exceedingly short duration and utilizing photoelectric pick-up apparatus. It is also an object ofthe invention to provide apparatus and methods oi indicating and recording the performance of ordnance projectiles and other rapidly moving objects. Another object is to provide improved circuit apparatus and methods, and sensitive photocell pick-up devices.

Other and further objects are those inherent in the apparatus hereinafter illustrated, described and claimed. l

The invention is illustrated with reference to the drawings in which teFigure 1 is a schematic plan view of the sys- Figures 2 and 3 are, respectively, front and side elevational views of a light source with its power supply and standard that is used in the system in conjunction with a photocell apparatus, illustrated in Figures and 6;

Figure 4 is an enlarged detail of the photoeleetric cell support;

Figures 5 and 6 show, respectively, front and sideelevational views of the sensitive photocell pick-up, self-contained amplifier and power supply and standard therefor;

Figure 7 is a wiring diagram of the light source and power supply therefor;

Figure 8 is the wiring diagram of the photocell and its associated amplifier;

Figure 9 is the wiring diagram of the power supply and output trigger tube apparatus of the photocell pick-up;

Figures 10 and 11 are, respectively, front and side elevational views of the indicating and recording instrument;

Figure l2 being a fragmentary vertical sectional view of a part of this apparatus taken along the line I2-I2 of Figure 10;

Figures 13 and 14, taken together, show the wiring diagram of the indicating and recording ss instrument, and the ,ampliera power supply. switching and testing apparatus therefor. Figure 13 should be placed at the left and 4Figure 14 at the right so as to show the complete diagram:

Figures 15 and -16 are, respectively, front and side, elevational views of the amplifiers, power supply, switching and testing apparatus; and

Figures 17, 18 and 19 are diagrammatic views showing, respectively, the Read," Range" and Disjuncture" operating condition switches I-X of the station unit.

Throughout the drawings corresponding numerals refer to the same parts.

General arrangement, Figure 1 Referring to the drawings, Figure 1 shows a schematic plan view of an illustrative installation. in this case speciiically an ordnance test nring range. The ordnance piece .undergoing-testing is shown at Il,`and may, for example, be a small arms riiie such as a 30 caliber or 50 caliber machine gun or a larger piece. 'Ihe rifle, if such be the ordnance piece undergoing testing. is mounted in nxed position and ilres down the range, along line I I-I I into a sandbag or other suitable bunker I2. Along the line of projectile flight there are two spaced pick-up stations, namely the muzzle station vI3 and the range station I4. `AI: the muzzle station there is a light source unit I I and a photocell and amplifier unit I8, and at the range station an identical light source unit 20 and identical photocell and ampliiler unit 22. The photocell units I8 and 22 and the light source units I8 and 20 are supplied with power by alternating current supply lines designated L1 and La. The output (signal) from the photocell-amplier I8 and muzzle station I3 is transmitted to the station unit 25 by means of a pair of signal lines K and G, line G being grounded as indicated at 26. Similarly the output (signal) of the photocell-amplifier unit 22 is transmitted to the station unit 25 by means of lines N and G', the latter being grounded at 21. The various units and their mode of interconnection and operation will be described in greater detail hereinafter.

Light source units 16 and 20, Figures 2, 3 and 7 The range and muzzle station light source units I6 and 20 are identical and are illustrated in Figures 2, 3 and '7. These units are made movable and include a base generally designated 30 to which is welded an upright standard generally designated 3|. Base 30 cousistsof a housing 32 adequately braced and provided with a iloor 25. The housing is preferably open at one side to reassai ceive a steel case 3l housing the power source o! the light, as hereinafter described. Case 80 is preferably made of strong metal. heavy walled. and may have a Ventilating grill 81 if heat losses are not adequately dissipated by radiation.

The upright standard is conveniently a simple steel channel 38 of U-shaped cross section having a pair of webs 8s and 4l welded thereacross to support the sockets 4| and 42 of the lumiline type lamp 43. A pair of conductors 44-40 are draped in the channel and are thus protected, the conductors extending down into the power supply case l.

`terminal of the primary winding 48 of transformer 50, and is also connected through lino 52 to the anode or anodes 53 of the rectifier tube 54. Line La is connected to the other terminal of winding 49 and thence through .iuctions l5, 88 and line 45 to the lumiline lamp 48, whence the circuit continues through line 44, to junction 51 and thence through iron cored reactor 8| and junction 58 to terminal 08 of the secondary 5| of the transformer. The filament (cathode) 65 of tube 54 is connected directly across the secondary winding 5|. Capacitors I8 and 80 are connected across the direct current output lines on either side oi the reactor 6|, as shown. In operation the transformer 50, rectifier I4 and the lter composed of capacitors 59 and 00 taken with reactor 6i serve to supply smooth direct current at appropriate voltage across lines 44 and 45, thus energizing lamp 48 so as to produce a uniform degree of illumination. Flashing oi the light or stroboscopic effects when lamps are energized from an alternating current line are thereby avoided. This is important in the very sensitive photoelectric application here illustrated.

The photocell units 8 and 22 occupy positions directly across from their cooperating light sources i6 and 20, respectively, as shown in Figure 1 and are positioned so as to intercept light from the lamp 43 of the light unit. Photocell unit i8 is arranged to intercept light projected in the direction of line 101|, while photocell unit 22 intercepts light in the direction of line 18-14. The lines of light 10-1I and 13-14 are across the path of night of the projectile, hence the movement of a projectile from the piece l0 towards f bunker I2 causes an instantaneous decrease in light falling on photocell |8 and a short interval later, depending upon distance D, Figure Land the velocity of the projectile, a similar instantaneous decrease occurs at photocell 22.

The time duration of these periods of decreased light intensity and the percentage variation in light intensity are both exceedingly small. Hence, a high degree of sensitivity and rapidity of response are requisite freedom from interference and accurate signal transmission. To accomplish these purposes there are provided the photocell, amplier and power supply units |8 and 22.

Photocell, amplifier and power supply units 18 and 22, Figures 5, 6, 9 and 10 For the purposes of the specifically illustrated embodiment of the invention. viz. ordnance testing, the photocell units I8 and 22 may be identical; hence only one need be described.

The combined photocell, amplifier and power supply unit I8 or 22 includes a base 15 and standard 18 of construction and dimensions similar to that yillustrated for the light source. The base 'il includes a housing 18 stiened with angle iron which may be open at one side to receive the power supply case 82, which is made of stout sheet metal and provided with grill Il. The case rests on the welded in door I5. Post 16 is of square or round hollow steel tubing, terminating in a boxlike ampliiier case 81 which has a front cover Il removably attached thereto. On top of the amplitler case 81 there is mounted a smaller steel cupola 80. An opening 85 from the top of the ampliiler case into the cupola is provided so as to allow the photocell which is mounted on the ampliner to be inserted. The cupola 80 has a light aperture 83, behind which is positioned the photocell. Case 8| forms a complete shield for the photocell, which is exposed to light only through window 88. Wiring from the power supply case 82 to the amplier case passes through the hollow post 'Ii and the support and wiring between the ampliiier and photocell passes through the small interior opening. not illustrated, between these cases. Each unit is thus completely shielded electrically and is so ruggedly mounted that sound and other mechanical vibrations produce no deleterious effects in the circuits. The light source units I5 and 20 and the photocell units |8 and 22 are painted black inside and out.

Figure 8 is a wiring diagram of the photocell and amplifier chassis which is mounted in case 88 and cupola 90. This unit includes a base 00 which physically supports two heavy walled boxes I0! and |02 which serve in turn as electrical shields and cases for the several amplifier stages. Boxes |0| and |02 are supported on sponge rubber pads |03 and |08 so as to damp out mechanical vibrations. Base |00 serves also to mount a connection socket |04 having terminals I through 8 which serve to connect the amplifier-photocell instrument, Figure 8, to the power pack and thyratron trigger tube unit, Figure 9. These terminals have the following purposes: Terminals and 8 supply illament current for the thrce amplifier tubes of Figure 8. Terminals 2, 4 and 6 are connected together and to ground through ground lines hereinafter traced. Terminal 3 supplies high voltage direct current (in this illustration, speciilcally 380 v. D. CJ. Terminal 1 supplies an intermediate direct current voltage (in this illustration, specically v. D. C.). Terminal 5 carries the signal output of the amplifler, Figure 8. to the gas-filled trigger tube (thyratron) in the unit, Figure 9.

The entire unit composed of base |00, shield boxes |0| and |02 and photocell |05 is housed in the box 81 and photocell cupola 80. Box 90 may be provided with an extra ground via line |08 to ground |01.

From the top of shield |0| there extend two copper tubes ||0 and which are positioned on shield |0| so that they will reach through port box 81 into the photocell cupola 80 when the chassis |00 is in place in the unit. Conduits ||0 and serve to support the photocell |05 and also serve as electrical shields for conductors |29 and |35 extending down from the photocell into the ampliiler. As shown in Figure 4, the conduits ||0 and are provided at their lower ends with female gland nuts H0 and III' which soldered to the center post ||3 oi socket ||1.

Lead wires |20 and |00 extend from terminals |20a and |00a (at the lower ends of conduits III and III) through the conduits and thence to terminals |20' and |30' on the socket. The photoelectric cell |05 is simply plugged into the socket ||1 when servicing or renewal is desired. It may be noted that conduits and extend up closely to socket terminals |20' and |00' but do not touch them, thus providing shielding as well as mechanical support to a position close to the socket, the mechanical support being then carried through post ||3.

` From the intermediate voltage direct current supply terminal 1, plug |04, line ||4 extends through resistor to terminalV ||0 whence the circuit continues along ground line ||0 through junction ||0|20. A branch of line ||0 extends to junction |21 which groundsline ||0 to case |0| and thence to ground terminals 2, 4 and 0 on plug |04. From variable positive tap |20 line |20 extends through junction |30 and through the conduit ||0 to the anode |00 oi the photocell |05. The circuit extends from the cathode |34 of the photocell through line |30 to junction |01 and thence through capacitor |30 to junction |30 which is connected by line |40 to control grid |43 of the pentode amplier tube generally designated |4|.

The tube |4| has a cathode |42 indirectly heated by lament |41, control grid |40, a second grid |44, a screen grid |45 and a plate |40. From junction |30 on line |40 a circuit extends through resistor |40 to junction |40 and thence to the negative terminal oi a bias cell |50. The circuit extends from the positive terminal oi' the bias cell |50 through resistor |5| to junction VI|0 on the ground line |0. A condenser |53 is connected from the negative terminal |40 of the bias cell to junction |20 on the ground line 0. From junction |01 a circuit extends through resistor |2|. thence through junction |3| to ground terminal H0. A condenser |32 is connected across terminals |00 and |3|, thus bridging the 'major part of resistor ||5.

From junction |2| on the ground line a circuit extends through line |54 to cathode terminal |55 and thence to the cathode |42 of ampliiier |4I. The screen grid |45 is connected to the cathode terminal |55. The second grid |44 is connected through line |51 to junction |50 and thence through resistor |50 to junction |00, from which the circuit extends through line |6| and condenser |62 to junction |24 on the ground line H0. From junction |50 on the lead |51 oi' grid |44, a circuit extends through line |00 to junction |54 and thence through a continuation oi line |03 and condenser |05 to junction |22 on the ground line ||0. 'To junction |04 therev is connected a resistor |01, the opposite terminal of which is connected to junction |23 on the ground line |0. The plate |40 of the ampliiler tube |4| is connected through line |00 to junction |10 and thence through condenser |1| and through resistor |12 to junction |20 on the ground line ||0. A circuit extends from junction |10 through resistor |13 to junction |14 and thence through resistor |15 and line |10 to the high voltage terminal 3 of the connection socket |04. Junction |14 is connected through line |10 to junction |00.

Amplifier tubes generally designated |00 and Y 8 220 are housed in the sheet metal box |02. Ampliner tube |00 has a cathode |0| indirectly heated by illament |01, a control grid |02, a second grid |03 and a screen grid |04 and plate |00. The control grid |02 is connected through line |00 which is shielded throughout its length by means of shield |00. The line |00 extends to a variable tap |00 on the resistor |12 of the ilrst l stage of amplification. The cathode |0| is connected through line |0| to terminal |02 and thence through the resistor |00 to terminal |05 on the ground line |04. The ground line |04 is grounded at |00 upon the metal case |02, the line |04 being extended to terminal 0 of the connector socket |04. From junction |02 a circuit extends through condenser 202 to junction |01 on the ground line |04. The second grid 00 and screen grid |04 are connected together externally and are connected through line 204 to Junction 205 on the plate lead 200. The plate lead 200 extends through junctions 205 and 201 and through condenser 200 and thence through line 4 200 and resistor 2|0 to Junction |00 on the ground line |04. From junction 201 on the plate lead a circuit extends through resistor 2|| to junction 2|2 and resistor 2|3 to junction 2|4 on the (high voltage) supply line 2|5 which is connected to junction |11 on line |10. A condenser 2 I0 is connected across junctions 2 |2 and ground terminal |00.

The third stage of ampliilcation is represented by amplifier tube 220 which has cathode 22| indirectly heated from iilament 222, a. grid 223 and plate 224. The grid 220 is connected to junction 225 on line 200, the cathode 22| being connected through line 221, junction 220, resistor 220 to terminal 200 on ground lead |04. A condenser 230 is connected around resistor 220 from junction 220 to ground terminal 20|. The plate circuit of tube 220 extends from plate 224 through line 23|, junction 232 and thence through resistor 234 to junction 235 and resistor 230 to high voltage supply via line 2|5. A condenser 230 is connected from junction 235 to ground terminal 20|. The output circuit of amplifier tube 220 is through condenser 240 and line 24| to terminal 5 on the socket |04.

Referring to Figure 0 there is illustrated the combined wiring diagram of the gas-filled trigger tube and the power supply chassis. The power supply serves not only that trigger tube 204 but also the amplifier and photocell circuits of Figure 8. The entire apparatus of Figure 9 is mounted on a suitable base and is housed within the box 02 on the base of the unit, Figures 5-6.

The incoming circuits to the unit of Figure 9 include an alternating current power supply lines L1 and Le which connects to a socket 242 of such construction that there can be no reversal of these leads since one of the leads (L1) is grounded. From terminal (line L1) 243, line 244 extends to primary winding 245 oi' transformer 245, from which the circuit continues through line 241, fuse 240, switch 240 to terminal 250 and line L1. 'I'he transformer has a lament winding 252, the center tap being connected by line 250 to housing ground 254. The outside terminals of winding 252 are connected by lines 255 and 255 to terminals l and 0, respectively, of the plug |04A which matches socket |04 of drawing Figure 8. Transformer 240 is provided with a plate voltage winding 251 and a filament voltage winding 20| which are connected to rectifier tube 202 in the customary manner as follows:

Winding 251 is connected to the two plates of the rectier and winding 26| to filament 263. The rectiiier negative output line 265 b connected to the midpoint 253 of transformer winding 251 and extends to the negative terminal 261 of the potentiometer resistor 269. 'I'he positive line of the rectier 262 extends from the filament secondary winding 26| through line 266 and extends through a choke coil 210 to the positive terminal 21| of the potentiometer resistor. A pair of condensers 212 and 213 are connected across the lines 265 and 266 and the chokes serve to smooth out the rectined direct current output.

The potentiometer resistor 269 is provided with tap 214 which is connected to the housing ground 254. The negative line 265 is, in the specific device here illustrated, approximately 40 volts negative. The resistor is also provided with a variable tap 215 of approximately 90 volts, a variable tap 216 of approximately 180 volts and a high voltage tap 211 of approximately 380 volts. Tap 215 is connected by line 290 to terminal 1 on the plug |04A and the high voltage tap 211 is connected by line 28| to terminal 3 of the plug. Terminals 2, 4 and 6 of the plug are oonnected together and are connected by line 262 to the grounded tap 214 of the potentiometer re- SiStOr.

A gas type trigger tube generally designated 234, having cathode 235, cathode heater lament 236, grid 231 and plate 268 is connected so as to be controlled by the incoming signals on terminal 5 of plug |04A. Terminal 5 is connected by line 230 to junction 29| and thence through resistor 232, switch 293, junction 294 to the control grid 261 of the tube. The cathode 235 of the tube is connected through resistor 296 to junction 291 on the ground line, resistor 296 being paralleled by the condenser 299. The resistor 296 is also arranged in parallel with a neon indicator light 300 which is connected through switch 30|. From tap 216 on the potentiometer resistor line 333 extends through resistor 304 to junction 305 on the plate circuit 306 of the trigger tube and the circuit continues over line 301. through condenser 303 and thence through junction 309 and resistor 3| 0 tojunction 3| on the ground line 232. Junction 309 serves as the output terminal and is connected by line 3|3 to the output terminal 3|4 on the output plug generally designated 3|5. A plug connection to socket 3|5 carries a ground line and a signal line. These are the pairs G and K or G' and N of Figure 1. Terminal 3| 6 of the output plug is therefore grounded at the station unit 25 and hence line 3|1 extending from socket 3|5, Figure 9, serves as a ground for that unit andalso for the parts shown in Figure 8 since these are al1 in the standard illustrated in Figures 5 and 6. Line 311, Figure 9, extends to junction 3|3 on the central tap lead 253 of the filament supply transformer, and thence through line 253 to junction 320 on the housing ground line 254. From junction 294 on the grid line of the trigger tube a circuit extends through resistor 322 to junction 323 on the ground line and from junction 29| of the grid resistor 292 a circuit extends through resistor 324 to a variable tap 325 on resistor 326. Resistor 326 is connected to junction 321 on ground line 202 and is connected through line 323 to the negative terminal 261 of the potentiometer resistor. A condenser is connected between junction 321 on the ground line and junction 330 on line 280.

Station apparatus The station unit 25 includes the apparatus 8 shown in Figures 10-12 and also the apparatus shown in Figures 13-16.

Figures 10, 11 and 12.*-Referring to Figures 10, l1 and 12 there is illustrated a unit having a base generally designated 335 on which is mounted a synchronous motor 336 which is coupled at 331 to the shaft 333, the latter being supported in a pair of bearings 339 and 343, Figures 11 and l2. To the front of the base 335 there is fastened a vertically positioned disk 342 which is attached in place by a plurality oi? cap screws 343. The disk 342 serves as a mounting for the bearing 343, Figure 12, and on the front end oi' the shaft 333 there is mounted a rotating unit generally designated 345. The unit 345 is of non-magnetic material and in its periphery is a groove which receives a very thin ring 341 of magnetic material which is fastened in place by any suitable means. 'I'he ring 341 of magnetic material serves to have impressed upon it the timing impulses.

On the front of the disk 345 there is mounted a dish-shaped cover 343 which serves to mount a neon lamp 349 on the inside which ls visible through a small aperture 350. The cover ls grooved at 352 and the groove is painted black so as to correspond with the black inside 353 of the housing in which the neon lamp is situated. One terminal of the neon lamp is grounded and the other terminal is carried out through lead 355 to a central stud 355 against which the spring contact 351 presses. Contact 351 is mounted upon an upright member 353 of clear plastic or any other suitable material so that the flash of the neon lamp will be visible through it. An incoming lead wire D is connected to the terminal 351 so as to conduct the incoming signal wave to the neon lamp.

The disk 342 is provided with a bushing 36| which serves as a hub for the adjustable radial arm generally designated 36| which extends out beyond the edge of the disk. The disk is provided with an arcuate groove 363 which extends about half way around the disk and through the groove there extends a stud 365 which passes through member 36| and serves as a support for another shorter member 366 that lies parallel to but be- I hind the member 36|. Another arcuate slot 364 may be provided if desired so as to allow a fastening rivet 363 to pass through the disk. Rivet 369 serves with 365 to fasten member 366 in spaced parallel relation with the outer part of radial arm 36|.

Between the protruding end 361 of arm 35| and 366 of arm 366 there is positioned a rubber roller 310 which is mounted on a shaft 312 held in place by a collar 313. On the front end of the shaft there is provided a manually adjustable knob 315. The location of shaft 312 is such that the rubber roller 310 presses against the edge 342A of the disk 342 and hence as the knob 315 is rotated, this causes the roller 31| to grip the periphery 342A and the members 36| and 366, as a unit, are moved arcuately around the disk. The periphery 342A may be knurled, if desired, to provide a good grip for the rubber roller.

Stud 335 serves as a support for a small electric coil 313, the core of which is shown at 319. The core terminates in a tip 330 which is very close to, but spaced from the magnetizable ring 341. Whenever an electrical signal is impressed upon the coil 316I the portion of the ring 341 which is then under the tip 330 is magnetlzed. The member 36| also serves as a mounting for the magnifying glass 33| which is located over a window in member 36| so that the graduations 342B will be readily visible therethrough. The map 9 AN k nifying glass is provided with a sighting line 332 ffltltsrnating' current for purposes of accurate reading. The coil 313 is energized through a lead wire 333 which extends out of the side of the coil and through the arcuate slot 333.

At another part of the disk 342 there is mounted a'second coil generally designated 333. The coil 333 is identical with coil 313 and is lprovided with a core terminating in a\ tip 333 likewise located very close to but slightly spaced from the vmagnetizable ring 341. Coil 333 is mounted upon a V-slot and has a sidearm 331 against which an adjusting screw 333 is adapted to bear. The adjusting screw is mounted in' the clip 339. As the screw 333 is turned the arm 331 is lifted or lowered and hence the coil 333 may be moved either way along the line of the double arrow 393. A scale 391 is located alongside the coil so that its position relative to the disk can be readily determined. The coil 333 is energized through an incoming pair of lead wires 393 which aretaken out through the end of the arcuate slot 333. An erasing coil 394 is mounted solidly upon the front of disk 342 and is provided with a core 395 extending close to but with slight clearance from the magnetizable ring. The erasing coil when energized with direct curany magetized signals on the ring 341.

Figures 13-14.-The electrical circuits of thev station apparatus oare illustrated in Figures 13 and 14. When reading these diagrams they should be arranged with Figure 13 to the left and Figure 14 to the right. The apparatus of Figures -12 is schematically illustrated at the right end of Figure 14 which shows the synchronous motor 333 driving the disk 343 upon which the neon lamp 349 is mounted. The fully adjustable or No. 1 pick-up coil 313 which is the movable one is likewise shown along with the No. 2 pick-up coil' 333 that is stationary except for slight adjustments occasioned by rotating screw 333. The erasing coil is shown at 394 and the neon light circuit connection at D. The synchronous motor is energized from alternating current lines L1 and La through switch 111, and the frequency meter 393 is connected across the lines. The frequency indication provides a basis for adjusting screw 333 and for thus imposing a slight movement of coil 335. The pick-up coil 318 is connected by means of its (shielded) cable 393 to station pre-amplifier No. 1 which is completely shielded by grounded housing 391. The shield of cable 333 is connected to this housing and the conductor to another portion, as later described. Similarly, pick-up coil 333 is connected through its shielded conductor 393 to station pre-amplifier No. 2, the shielding of the cable being connected to grounded case 393 which likewise serves to shield the pre-amplier. The internal lead of vthe cable 393 is connected to the pre-amplifier No. 2 as later described.

Referring to Figure 13, under the bracket generally designated 433 there is villustrated what may be described as the thyratron chassis. In this portion of the apparatus there is included two power supplies, two gas type trigger tubes (thyratron) and a plurality oi switches, preferably of the microswitch type, that are manually operated, as hereinafter described. Under the bracket 431 there is illustrated a power supply No. 1T while over the bracket 432 there is illustrated an identical power supply No. 2T. Since these power supplies are identical only one need be described as representative.

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supply is provided over lineslaandhandswitchlwhichservesto energize the primary winding 433 of the transformer generally designated 433 and also that of I power supply No. 2T. It may be noted incidentally that all alternating current service lines to the installationk maybe served through this one switch, if desired. or separate controls may be used. The transformer 433 has a secondary 433 which serves through switch 123 .to feed the iliamentcathode 431 oi' the full wave rectifier tube 433. The transformer also has a higher voltage secondary 439 which is connected to the two anodes 413 and 41| of the full wave rectifier tube 433. The positive output line 412 is connected to one side oi the transformer winding 433 and the negative output line 413 is connected through switch 121 to the center tap 413 of the winding 439. Choke coil 413 and a pair of condensers 411 and 413, connected in the usual way, serve to smooth out the direct current 'output which is applied to a potentiometer resistor 419 having an intermediate ltapf423 grounded at 421. The tap 422 is apprpximately 20 volts negative and the tap 423 approximately 400 volts positive.

, Similarly. power supply No. 2T. shown over the bracket 432, provides approximately 20 negative volts on negative output terminal 424, ground potential at tap 423 and approximately 400 volts positive at output terminal 423. A direct current voltmeter 421 having one terminal grounded at 423 is arranged to be connected through switch '|14to positive output terminals 423 and 423 of the two power suppliea'in order to read either of the output voltages. An intermediate voltage tap 433 is provided on the potentiometer resistor 43| of power supply 432 and is connected through switch 432 to junction 433 and thence through resistor 434 to lead 433 which ellrtends to the eraser coil 394, Figure 14. A ground lead 433 is connected to condenser 431 and also extends to the eraser coil. By closing switch 432 for a short time, condenser 431 is charged to the voltage of tap 433 on power supply 432. This potential is also applied through resistor 434 and lead wires 433 and 433 to the eraser coil 394.

When the push-button switch 432 is opened, condenser 431 discharges through the resistor and the eraser coil. and the magnetism of this coil therefore subsides to nero value, in a time period determined by the time constant'of this circuit. During erasing the disc 343 is rotated and hence a gradually d magnetism is applied to the disc for the erasing operations.

Microswitches.-At the right-hand portion of each of Figures 13 and 14 there are shown a plurality of microswitches designated I-VI in Figure 13 and VII-X in Figure 14. Each of these switches has two operative positions. Switches I-VI are operated mechanically by means of cams through asingle cam-actuated shaft controlled by the operator through a suitable handle 113, Figure 15. There are three sets of operating conditions for switches vI-VI, as shown by Figures 17, 18 and 19. Microswitches VII and VIII are operated by an alternating current solenoid actuator Va. which is in turn energized by microswitches V. Switches IX and X are operated through an alternating current solenoid actuator Vla controlled by microswitch VI. The circuits for the solenoid actuators are as follows:

Alternating current is supplied through lines L1l and Le (at the center of Figure 13). Line Li is connected to feeder 433 which extends to junc- 11 tion 438 and thence to the common terminal 445 of switch V, another extension being to the common terminal 44| of switch VI. When switch V is in the position shown in Figure 13 (same in Figure 17), a circuit is completed to terminal 442, switch V, whence power is conducted by way of line 443 to 'the winding of the solenoid actuator Va, the return circuit to line I c being by way of line 444. Thus, when switch V h in the position shown in Figure 13, the coil of solenoid actuator Va is energized and the microswitches VII and VIII are held in the position shown ln Figure 14. Switches VII and VIII are located within the shield 581 of pre-amplifier No. 1 and are thus isolated from extraneous electrical disturbances from coil Va or anything else. When switch V is moved against contact 445 the circuit to coil Va is broken and microswitches VII and VIII move to the opposite position from that shown in Figure 14. Similarly when microswitch VI is in the position shown in Figure 13 (same for Figure 17) a circuit is completed from line L1 through junction 438 to terminal 44| and thence through microswitch VI to terminal 446 whence the circuit continues by way of line 448 to the coil of solenoid actuator VIa, the circuit being completed to line La by way of line 444. Thus, energizing the solenoid actuator VIa holds microswitches IX and X in the position shown in Figure 14. When microswitch VI is moved to the position so that its movable contact engages the dead contact 441, the circuit to coil Vla is de-energized and the microswitches IX and X move to the position opposite to that shown in Figure 14, see Figure 18, for example.

There are three sets of operating conditions which are shown in Figures 17, 18 and 19, these three conditions being the reading conditions for the instrument marked Read," Figure 17, the condition under which the signal from the range photocells are impressed upon the station apparatus marked Range, Figure 18, and a testing condition under which certain tests of the instrument itself are made marked Disjuncture, Figure 19.

The signals from the muzzle and target range stations I8 and 22, respectively, are received by way of lines K and N (Figure 1) which terminate at microswitches I and 1I, respectively, Figure 13. Incoming ground lines G and G' of Figure 1 are not illustrated in Figures 13 and 14. Thus, line K is connected to terminal 448 of microswitch I and when that switch is in the Range or Disiuncture positions, Figures 18 or 19, the circuit is completed to the common terminal 455 of the microswitch I, and thence through resistor 45| and condenser 452 to the primary 453 of the transformer generally designated 454. The circuit is conmpleted to ground line 455 which is grounded at 456. The received signal from the range stations (either the muzzle or target stations) is a sharp negative wave and this induces a similar sharp positive wave in the secondary 451 of transformer 454. Secondary 451 is connected by line 458 to the negative terminal 422 of power supply No. 1T which normally maintains a negative voltage on the transformer secondary, and is also connected directly to the grid 465 of a gas type trigger tube (preferably thyratron) generally designated 45|, Tube 46| is provided with an indirectly heated cathode 452, grid 465 and anode 463. The anode is connected by means of line'464 and condenser 465 to the ground line 455 and is connected through line 461 and resistor 481 to the positive termi- 12 nal 425 of power supply No. 1T. The transformer secondary 451 is also connected through condenser 455 to the ground line 455 which supplies a high frequency pass for the sharp wave signal induced in the secondary. Cathode 452 is connected through the primary 415 of the transformer 41| to ground line 455. The trigger tube 45| is ordinarily not conductive and the condenser 455 charges to the voltage of output terminal 425 by means of the charge line 451 in which there is located the resistor 451.

The grid 455 of the trigger tube is normally maintained negative through transformer secondary 451 and the connection 455 to the negative terminal of the power supply. When the sharp negative signal wave is impresed upon winding 455, this induces a positive signal at winding 451 which momentarily shifts the grid 465 to the positive condition, whereupon tube 45| becomes conductive and remains conductive until the charge on condenser 455 is dissipated, whereupon it ceases to conduct since there is no longer any appreciable voltage existing across the condenser 465. Resistor 451 is of high enough value that it will not supply current for continuing the discharge.

This momentary discharge surge is impressed upon the primary 415 of the transformer 41| and induces a signal current surge in the secondary 413 of that transformer through a circuit extending from ground 456, through ground line 455, thence to terminal 414 through the secondary 415, line 415, terminal 416 to theanode 411 of the full wave rectifier tube 418, thence to the cathode 418 of the rectier tube and to the terminal 455 of the cathode heater supply transformer. The circuit continues through resistor 45| and line D to the neon tube 548 on the revolving disc and thence to ground. Thus, an incoming signal from the photocell at the muzzle range station I8 produces a momentary flashing of the neon light on the rotating disk 845, To junction 415 (see Figure 13 near transformer 41|) there is connected a resistor 453 which is connected to the ground line 455 at junction 484. The cathode of the full wave rectifier tube 415 is powered by secondary winding 485 of transformer generally designated 455. The primary 481 of the transformer is connected to alternating current feeders 458 and 444.

In an analogous manner, a signal received on line N from the photocell station located at the target range station 22 is applied to terminal 485 of the microswitch II. When the microswitch is in the "Range position, Figure 18, the signal is communicated to microswitch terminal 485, whence the circuit continues through resistor 45| and condenser 482 to the primary 455 of a transformer generally designated 454, and thence to ground line 455. One terminal of the secondary 485 of the transformer is connected by line 485 to the negative terminal 424 oi' power supply No. 2T shown over the bracket 452 and is likewise connected through condenser 481 to the ground line 455. The opposite terminal of the secondary 485 is connected directly to the grid 455 of the gas-filled trigger tube 488. This trigger tube is identical with that illustrated at 45| and includes an indirectly heater cathode 555, grid 485 and anode 55|. The anode is connected through line 552 and resistor 558 to the positive terminal 425 of power supply No. 2T and is connected through condenser 555 to the ground line 455. The cathode 555 is connected through the primary 555 of the transformer 551 to the ground line 455. The secondary 555 of transformer 551 is grounded at 13 Junction v414, the opposite terminal being connected through line 555 and junction |5 to the anode 5|2 of full wave rectiilertube 413. A resistor 5|3 is connected between junction 5|5 a'nd Junction 454 on the ground terminal,

Thus, when a signal is received from the target range station 22, the sharp, negative wave received on line N is communicated through the microswitch II to the transformer primary 453 which serves to induce a similar sharp positive wave in the transformer secondary` 455, thus swinging the normally negative grid 493 of the trigger tube 459 to the positive condition causing that tube to become conductive. -This causes the charge on condenser 555 to be dissipated through '14 The anode 552 of the pcntode tube 545 is connected by line 533 through Junction 554, condenser 535 and resistor 555 to the ground line.

the primary 555 of the transformer 551. thereby light being grounded at the disk.

In Figure i4 the upper and lower parts of the diagram include two amplifiers, ampliiler No. 1

under the bracket 5|5 and amplifier No. 2 over the bracket 5|5. Each of these ampliiiers includes a pre-amplifier section, namely pre-ampli- !ier No. '1 and pre-ampliiler No. 2. The preamplitlers are housed in grounded, shielded cases shown by the dotted line outline 391 and 395 previoly referred to..

Referring to ampliner No. 1, a power pack, not illustrated, is connected across'the potentiometer resistor 5|1l through switch 135. The resistor has a ground at 5|5 and has a negative terminal 519 of about 110 volts negative, a 12S-volt positive tap at 525, a 180-volt positive tap at 52| and a 240- volt positive tap at 522 which is the positive output terminal. A bridging resistor 523 is con- `nected across the ground and negative terminals and is provided with an intermediate voltage tap 524. I

The input to the pre-amplifier section of ampliiler No. l is by way of the shielded cable 333 which is connected to the terminals 525 and 525 of microswitchesVII and VIII, respectively. Contacts 521 and 525 of these microswitches are grounded. Movable contact 525 of microswitch VIH is connected via line 535 to the movable contact 532 of microswitch III. The movable contact 535 of microswitch VII is connected to one terminal of the primary winding 534 o! the transformer 535, the other terminal of that winding being connected to ground line 545. The secondary winding 531 is connected to the ground line 545, and the opposite terminal is connected through junction 54|, inductance 542 and junction 543 to the control grid 545 of the pentode amplifier tube generally designated 545.

Tube 545 includes a cathode 541 which is connected through junction 545 to the suppressor grid 549 and from junction 548 there is a parallel circuit composed of resistor 555 and condenser 55| extending to the ground line 545. A pair of condensers 552 and 553 are connected from junctions 543 and 54 I, respectively, to the ground line 545. The grid 554 is connected through condensers 555 and 555 in parallel to the ground line 545 and'is connected by way of junction 559 and through resistor 559, junction 555 and line 55| to the positive terminal 522 of the power supply.

vpositive terminal 522 on the power supply.

The four-element amplifier tube generally des- :ensued m includes an indirectly heated cathode 515. a control grid 51|, second grid 512 and anode 513. The cathode 515 is connected through iunction 514 and through resistor 515 and condenser 515, in parallel. to the ground line 545. The grid 512 is connected through line 511 to tap 525 of the power supply. Anode 513 is connected to Junction 519 and thence through resistor 555 to tap 52| on the power supply. 'I'he grid 51| is connected to a variable tap 55| on resistor 555 by which the gain of this tube may be varied. Prom 519 a circuit extends through condenser 532 kto Junction 583 and thence through resistor 554 to variable tap 524 on resistor 523. The variable tap 524 regulates the bias of tube 555.

' Tube 555 is a. gas-illlcd trigger tube of the thyratron type and includes an indirectly heated cathode 555, control grid 551 and anode 555. The grid 551 is connected through resistor 559 to junction 553 and cathode 555 is connected through line 595 directly to ground line 545. The

anode is connected to Junction 59| whence a circuit extends through resistor 592 to tap 52| on lthe power supply. From junction 59| a circuit also extends through 'condenser 593 and resistor 554 to ground line 545. From tap 595 a circuit extends to contact 595 of push button controlled microswitch B. The microswitch B also includes a contact 591 which is connected by way of line 555 to junction 599. 'I'he movable contact 555 of the push button controlled microswitch B is connected by line 55| to contact 552 of cam controlled microswitch I.

From junction 59| a testing circuit extends via line 553 through normally open switch 554 and thence through resistor 555 and neon light 555, in parallel, and through condenser 551 to ground line 555.

Amplifier No. 2 shown over bracket 515 is of precisely the same type as amplier No. 1. The input to the preamplifier portion of amplifier No. 2 is byway of shielded cable 993 which is connected to contacts 559 and 5||| oi microswitches IX and X, respectively. Contacts 5|| and 512 of these microswitches, respectively, are grounded. Movable contact 5|4 of microswitch IX is connected by means of line 5|5 to movable contact 5|1 oi microswitch IV, Figure 13. Contacts 515 of microswitch III and 5|9- of microswitch IV are connected together and grounded at 525. Contacts 52| of microswitch III and 522 of microswitch IV are likewise connected together and to line D at Junction 523.

'Ihe movable contact 525 of microswitch X is connected to the primary 525 of transformer 521. The primary 525 is connected to ground line 525. The secondary winding 590 of the transformer and condenser 53| are connected .in parallel at junction 532 and are connected to ground line 523. From junction 532 the circuit extends through inductance 533 and thence to the grid 15 Y denser 642, in parallel, to ground line 626. Fro anode 643 a circuit extends over line B44 to Junction 046 and thence through condenser 646 and resistor 441 to ground line 626. From junction 64I a circuit extends through resistor 649 to junction 660 and thence over line 66| to the positive terminal |62 of the potentiometer resistor 663. The potentiometer resistor is supplied through switch 134 from'an independent powerpack of the type described with reierence to amplifier No. 1. llrom' grid 664 o! pentode 635 a circuit extends through Junction 666 and 666 and through condenser 661 to the ground line 626. A condenser 660 is connected between junction |66 and ground and s resistor 669 is connected between Junction 664 and 660, and thence over line 66| to positive terminal 862.

The tetrode amplifier generally designated 660 has an indirectly heated cathode 66| which is connected through resistor 662 and condenser 663 in parallel to ground line 626. The control grid 664 of the tetrode, is connected to the variable tap 665 of resistor 641 by which the gain of the tetrode amplifier is regulatable. The grid 666 is connected to tap 661 on resistor 653, and the anode 668 is connected through junction 669 and resistor 610, junction 61| to tap 612 on the resistor 653. Junction 669 is connected through a condenser 613 to junction 614 from which a circuit extends through resistor 615 to variable tap 616 on the bias resistor 611. The bias resistor is connected to the ground tap 618 and to the negative terminal 619 of the potentiometer resistor 653, and by varying the adjustment of the tap 616, the bias of the tetrode 660 may be varied. From junction 614 a circuit extends through resistor 680 to the grids 68| of the gas-lled trigger tube 682. The trigger tube has an indirectly heated cathode 683 connected to the ground line 628 and an anode 684 that is connected to junction 685. From junction 685 a circuit extends through resistor 681 to junction 61| and thence to tap 612 on the potentiometer resistor. Likewise from junction 685 a circuit extendsthrough condenser 689 to junction 690 and thence over line 69| to junction 599 from line 69| and continues to terminal 692 of microswitch II. From junction 690 a. circuit likewise extends through resistor 693 to the ground line 628.

From junction 599 a circuit extends to terminal 694 of the push botton operated microswitch A. Microswitch A has a movable contact 695 which is normally maintained in contact with the stationary contact 696 from which a circuit extends through resistor 691 to tap 698 on the potentiometer resistor 653.

The disjuncture charge circuit, shown over the bracket 100, consists of a resistor and a condenser 102 connected in parallel between junctions 103 and 104. Junction 103 of the parallel circuit is grounded and junction 104 is connected to the movable contact 695 of the push button operated microswitch A.

From junction 685, Figure 14 (the output of amplifier No. 2), a circuit extends over line 105, through normally open switch 106 and thence through resistor 101 and neon light 108, in parallel, and through condenser 109 to ground line 608. Both the neon lights 606 and 108, together with their parallel resistors and a control switch, are testing circuits as indicated.

Figures 17, 18 and 19.- These gures show the position of the manually operated microswitches I throughV'Iandthesolenoidoperatedmicroswitches VII through IX in the three operating conditions ofthe system, namely a "Read position (Pigure 17) when the` recorded signals are read, s Range position during which the signals are received from the range and recorded on the magnetic element of the revolving disk and a Disjuncture position which is a circuit testing condition.

Figures 15 and 16.-The circuit apparatus Just described may be embodied conveniently in a panel type mounting as shown in Figures 15 and 16. This mounting includes three main panels- 1I0,1|| and 1|2. Panel 1|| is provided with a manually operable handle 1|3 which serves.A

through suitable cams not illustrated, to oporate the microswitches I through VI. causing them to close the circuits as shown in Figures 13 and 17, 18 and 19. The three operating positions Read Range and Disiuncture" are shown on the front of panel 1| Panel 1| I also includes the double throw switch 1I4 and the meter 421 serving power supplies Nos. 1T and 2T.

Panel 1 i0 includes a voltmeter 1|6 which indicates the alternating current supply line voltage and a number of control switches 1|1, 1 |6, 1|l, 120,12I, 122 and the push button 123. This panel also includes a number of pilot lights 124, 126, 126, 121, 128 and 129. The purposes of these are ls follows: Switch 1|1 controls motor 336 and pilot light 124 indicates when the circuit is in operation. Switch 122 is the general alternating current control switch and pilot light 126 its indicator. Switch 1|8\ controls the plate circuit of tube 499 and switch 1|9 the filament, These tubes require a long warm-up period. Pilots'126 indicate plate voltage and pilot 121 filament current of tube 499. Switches and 12| control the 11iament and plate voltages of tube 46|, respectively: pilot light 128 indicates the filament current and pilot light 129 indicates the plate voltage of said tube 46|.

Panel 1|2 includes a meter 130 (see Figure 14) which indicates the voltage from ground to terminal 522 (power supply of amplifier No. 1) and from ground to terminal 662 (power supply of amplifier No. 2). Meter 130 is connected through a double throw toggle switch 429, as shown in Figure 14, in order to read either voltage. This panel also includes a toggle switch 134 for turning ofI and on ampliiler No. 2, a toggle switch 13| for turning off and on amplifier No. 1. Switches 135 and 134 are not shown in Figure 14 as they control the alternating current feed to standard rectifier power packs (not illustrated) which in turn are connected to potentiometer resistors 6|1 and 653. The energization of ampllner No. 1 and amplifier No. 2 is thus controlled by turning on or o the alternating current feed lines to the power packs feeding these amplifiers. Pilot lights 132 and 13| are connected to the power supplies of amplifiers No. 1 and No. 2, respectively, to show energization when switches 136 and 134 are closed.

At the bottom of panel 1|2 there is an adjustment knob 136 which controls the "gain" regulatcontrols the gain regulating contact 56| of amplifier No. 1 and a control knob 133 for varying contact 524 of the bias control of amplifier No. 1. Push button controlled microswitches A and B that are used in the disjuncture test operation 75 are also included on panel 1|2.

of the appropriate control switches, the light sources |3 and 20 are illuminated and light falls upon the photocells |05 in each oi the photocell and amplifierunits |0 and 22. When the ordnance piece |0' (Figure l) undergoing testing is nred. the projectile travels along the line |II| andv as it passes the line of sight --1I at the muzzle station in the range, light from the light source I6 that has been i'alling'upon the photocelland amplifier I8 is thus momentarily decreased in amount. As the projectile passes the line -13-14 at the target station the light from light source 20 that hasbeen falling upon the photocell |05 in unit 22 is likewise momentarily decreased in amount.. The photocells and their amplifiers operate upon decrease in light. The percentage decrease is very small. Referring to Figure 8, under normal illumina tion the photocell |05 has a steady current conducting effect and the potential existing between Junctions ||8 and |28 (lower left in Figure 8)` causes a steady. current ilow from junction |28 through line |29 and photocell, thence through line |36 and Junction |31, resistor |2|, junction |3| to junction ||6 on ground line H8. When the photocell is illuminated steadily, amplifier tube |4| is conductive at a constant value. When the photocell is darkened due to the passage of the projectile, the amplier tube |4| momentarily becomes less conductive. Under normal steady state conditions curren-t flows from high voltage supply, i. e., contact 3 of the socket |04, through line |16, resistors and |13, junction |10, line |69, plate |46. cathode |42, line |54 to ground line ||8. The degree of conductivity of the tube is determined by the 'negative bias on grid |43 as determined by the bias cell |50. When the illumination falling on the photocell momentarily decreases, the resistance of the cell increases, and there is accordingly a momentary negative voltage wave at junction |31 which is impressed through condenser |38 upon grid line |40 of -tube |4|. This causes the tube |4| to become less conductive (of greater resistance) and hence the current flowing in its cathode-anode circuit decreases. This produces `a momentary positive voltage wave at junction |10 in the plate circuit, and this is impressed through condenser |1| upon resistor |12 and is conducted through line |88 to grid |82 ofthe amplifier tube |80.

Amplifier tube |80 which is normally conductive at a steady state becomes more conductive due to the positive wave impressed upon its control grid |82. The output circuit of tube |80 extends from terminal 3 of socket |04, through line |16 to junction |11, then through line 2|5, junction 2|4, resistors 2|3 and 2||, line 206, to plate |86, cathode |8| and through resistor |93 to ground line |94. The momentary increase in conductivity of tube |80 (which is equivalent to a momentary decrease in resistance of the tube) has the effect of producing a negative voltage wave at `junction 201 in the plate circuit 206, and this is impressed through condenser 208 upon line 208 and through it to the control grid 223 of amplifier tube 220.

Amplifier tube 220 is normally conductivev through-a circuit extending from terminal 3 of socket |04 and through high voltage lines |16 and 2|5, through resistors 238 and 234, line 23|, plate 224, cathode 22|, and resistor 223 to ground line |94. The momentary decrease in conduc- 18 tivity o1' the tube 220l (which is equivalent to a momentary increase in resistance of Ithe tube) has the eii'ect of producing a positive output wave 'at junction 232 in line 23| as the signal comes through. The output positive wave is impressed through condenser 240 upon line 24| and thence to output terminal 5 of the plug |04A.

Before tracing through the energization o! signal inthe circuit shown in Figure 9, it may be pointed out that in ordnance testing Vthe wave shape of the signal is equivalent to a relatively high frequency output and that various low frequencies are objectionable. Despite many safeguards against -the introduction of low frequencies from the commercial (60 cycle) supply, some signals of this character are present in the circuit. Likewise the muzzle flash of the ordnance piece undergoing testing and explosion ash where an explosive projectile is tested, produces light signals which to some degree ilnd their wayA into the photoelectric apparatus, and these likewise produce signals"of lower frequencies. In order to discriminate against these signals and to favor the desired relatively higher frequency signals, condenser 208 (between tubes and 220) is of small capacity. This condenser with resistor 2|0 may be -considered as a high pass filter which discriminates against the lower frequencies. Thus, even in the ampliiler shown in Figure 8 which is mounted directly below the photocell in the physical apparatus (Figures 5 and 6) provision is -made for discriminating against further transmission of the undesirable lower frequencies.

The positive output signal wave on terminal 5 I is communicated through the plug |04`|04A to line 280 of Figure 9 and thence through resistor 292 and normally closed switch 293 to the con-trol grid 281 of the gas-filled trigger tube 204. The grid 281 of tube 284 is connected through resistor 322 t-o the housing ground line 282. The resistor 324 which is connected to the grid lead at 29| -and to tap 325 of the power supply normally maintains Ithe grid 281 negative through resistor 292. The variable tap 325 is adjusted so as normally to maintain the grid 281 negative by an amount slightly less than the incoming positive signal wave on line 290 and hence when the signal is received the grid 281 momentarily swings positive and tube 284 ilres through a circuit extending from positive Itap 216 on the power supply potentiometer resistor 269, thence through resistor 304, junction 305, anode 288, cathode 285, resistor 296 to ground line 282. Tube 284 which thus becomes momentarily of very low resistance serves to discharge condenser 308 through a circuit extending from ground line 282, resistor 3|0, condenser 308, line 301, junction 305, through the anode-cathode circuit of tube 284, resistor 296 to ground line 282. very short duration occurs at output terminal 309 and is communicated through line 3|3 to output terminal 3 4 on the plug 3 5.

While tube 284 is non-conductive prior -to firing. no current ilows through its anode-cathode circuit, and hence there is practically no potential drop across resistor 296 in its cathode circuit, but

when the tube 284 becomes conductive and fires,

there is a relatively large potential drop -across resistor 296. This has the eifect of immediately stopping the ilring oi' the tube.

It may be pointed out also that most of the current flowing through the tube when it res is from condenser 308 due to the relatively high value of resistor 304 and that when switch 283 is open, the tube will nre periodically at a rate de- When this occurs a wave of 19 termined by the size of condenser 333 and resistor 334. This serves as a convenient means of testing the operation of the gas tube apparatus since merely by opening switch 233 it is possible to impress upon the output 333 a series oi repeated, sharp negative waves. Any deviation from this normal testing response clearly indicates some erroneous operation of the apparatus. Likewise, when 'switch 293 is opened the input signal on terminal may be tested conveniently by connecting an oscilloscope to the oscilloscope jack 332. The spring terminal 333 of the jack is connected through line 334 to the input signal terminal 5 of plug |34A, the other terminal 335 of the jack being grounded. Thus, by connecting an oscilloscope to jack 332, it is possible to test the incoming signal received at the apparatus of Figure 9 which, in the physical embodiment, is in the base 82 of the stand.

At the station unit 25, Figure 1, the incoming signal from the muzzle photocell and amplifier station i8 is received over line K, and the signal from target station is received over line N. Since it is assumed that the handle 1|3, Figure 15, has been moved to the Range position, microswitches I through VI are thereby manually positioned as shown in Figure 13 (same in Figure 18) and microswitches V and VI thereby control microswitches VII through IX to the corresponding positions as shown in these gures. The signal received upon line K (Figure 13, upper center) is thereby impressed through resistor 45| and condenser 452 upon the transformer primary 453. The incoming signal is avery steep negative wave front and this induces a steep positive Wave front in the secondary 451 of the transformer 454 causing the grid 463 of the gas-filled trigger tube 46| to be swung momentarily positive. Tube 46| thereupon becomes conductive and serves as a discharge path for the charge stored upon condenser 465 as previously explained. The sharp surge through the tube 46| passes through the primary 410 of transformer 41| thereby inducing a signal in secondary winding 413 which is transmitted through rectifier tube 418, line D and the microswitches to the No. 1 pick-up coil 318 adjacent the rotating disk 345 through a circuit as follows: From ground 456, Figure 13, a circuit extends through line 455, junction 414, secondary winding 413, junction 416, through line 411 to cathode 419 of tube 418, thence through junction 480, resistor 48|, line D to junction 623. The line D from junction 623 extends to the neon light on the revolving disk and hence the light is iiashed but this is incidental to the recording of the signal on the disk 345 for the circuit branches at 623 on line D and extends to contact 62| of microswitch III and to contact 622 of microswitch IV. Since the movable contact 6|1 of microswitch IV is in engagement with contact 6|9 (that is grounded at 623), no circuit is completed from contact 622 of microswitch IV, but a circuit is completed from contact 62| of microswitch III, through movable contact 532 and thence over line 530 to movable contact 523 of microswitch VIII which is then in the position to engage its contact 526 from which the circuit continues over shielded cable 383 to No. 1 pick-up coil 318, which now acts as a recording coil and produces a magnetic signal on ring 341 of disk 346. It may be noted that at this time movable contact 536 of microswitch VII is in engagement with its ground contact 526 thereby preventing any leakage of the high frequency signals across into the pre-amplier of amplifier No. 1 which `might. occasion erroneous operation of that am- As the projectile passes line 13-14 at the target station it actuates the photocell and amplifier 22, Figure 1, thereby initiating a signal which comes into the station unit 23' via the "target line N, Figure 13. Since microswitch II is in engagement with its contact 433, the sharp, negative wave signal is impressed through resistor 43| and condenser 432 through the transformer primary 433 to ground line 453. 'This induces a sharp positive wave in secondary 433 ot transformer 434, thus initiating the discharge through the gas-illled trigger tube 433, in exactly the same manner as for tube 43|. The charge upon condenser 335 which had been built up through resistor 333 during the time tube 433 was non-conductive, is thereby discharged through tube 433 and through the primary 333 of transformer 531.l Consequently, a voltage is induced in secondary 533 which' is conducted through rectier tube 413 to junction 323 of the line D, where it is distributed to the neon light 343 causing it to ilash and also through microswitch III to No. 1 pick-up coil 313. This causes the energization of the pick-up coil, which, acting again in its recording capacity, makes a second magnetic record on ring 341 of disk 343. Since the disk is rotated by the synchronous motor 333, the passage of the projectile thus causes two magnetic records to be recorded on the magnetizable rings 341 of the disk 343 at angular spacings determined by the speed of the disk and the speed of the projectile. The record may be played back by moving the operator handle 1|3 to the Read position.

Read position-With the handle 1|3 in the Read position, microswitches I-VI are moved to the position shown in Figure 17 and in that position the switches V and VI actuate switches VII-X to the positions also shown in Figure 18. It will be recalled that both of the magnetic records on the rotating disk 346 were impressed by means ot No. 1 pick-up coil 318. As the disk rotates, however, the magnetic records on the disk serve at each revolution to induce slight electromotive forces in both of the pick-up coils 318 and 385. Whenever a voltage is thus generated in one of these coils, it is ampliiled either through amplifier No. 1 or ampliiler No. 2, depending upon the pick-up coil in which the voltage is generated. ASince the action is identical for both pick-up coils and ampliner, only one need be described.

Assuming that the leading magnetic record passes under No. 1 pick-up coil 313, the voltage thus generated is transmitted by way of shielded cable 383 through microswitches VII to primary 534 of transformer 535 which induces a voltage in secondary 531 that is applied to the grid of tube 546. The incoming signal from the pick-up coil is an approximately symmetrical wave, but tube 548 is biased so that the output in its plate circuit 563 is predominately negative, the positive portion of the wave being suppressed at least in part. The output oi tube 543 is transmitted through condenser 365 and resistor 533 to the grid 51| of tube 563. Then tube l563 is normally conductive but becomes less so when the negative signal is applied to its grid 31| thus causing a positive signal at junction 513 which is transmitted through condenser 332 to the grid 531 of the gas-filled trigger tube 535. It may be pointed out that as in the photocell amplifiers (Figure 8) condenser 332 serves to suppress the 21 A lower frequencies and accordinglythe control voltage on the grid 581 of the trigger tube is very sharp. The trigger tube 585 is normally non-conductive but becomes conductive due to the incoming signal on its grid 581. The discharge through tube 585 is principally from the condenser 593 since resistor 592 is of a sufficiently high valuey that insufficient current is passed to maintain discharge of the trigger tube. Accordingly, as'the charge on condenser 583 is dissipated tube 585 again assumes the non-conductive condition.` The discharge of condenser 593 accordingly generates a very sharp negative voltage at junction 595 which is conducted throughthe normally closed push buttoncontrol microswitch B and through microswitch I, resistor 45|, condenser -452 and primary winding 453 of transformer 454 to ground. This induces a signal in the secondary 451 which eventuates in the operation of the noon light 449 on the revolving disk 445 through an operation precisely the same as when the incoming signal is received from the range, as previously-described. Thus, as the leading magnetic record passes under the No. 1 pick-up coil, the neon light is caused to flash.

Similarly the trailing magnetic record passes under No. 1 pick-up coil and likewise causes the neon light to flash but since the disk has now proceeded around through an angularity equal to the angularity between the magnetic records on the disk, the neon light flashes occur in angularly disposed relationship. It will be assumed that the adjustment of knob 315 is such that No. 1 pick-up coil is located at an angle in respect to the No. 2 pick-up coil which is greater than the angle between the magnetic records on the disk 341. When this is true, the trailing magnetic record approaches the No. 1 pick-up coil and causes the second signal flash before the leading magnetic record passes under the No. 2 pick-up coil. A third flash occurs when the leading magnetic record passes under No. 2 pick-up coil, and the third flash occurs at an angle from the second flash which is equal to the difference between the angle between the pickup coils and the angle between the magnetic flashes. Thereafter, as the trailing magnetic record passes under the No. 2 coil, a fourth flash occurs. By rotating the knob 315` so as to decrease the angle between the pick-up coils, the two middle flashes (second and third) are brought gradually together until they coincide. When this occurs the operator knows that the magnetic coils are set at the same angle as the magnetic records on the rotating disk and by simply reading the angularity on scale 342B and knowing the rotary speed of the magnetic disk, it is possible to calculate the time elapsed between the flashes. Usually, the scale 342 is calibrated directly in feet per second for convenience.

The recording and reading presupposes a constant frequency impressed upon the driving motor 335. In order to provide for correction if the frequency varies, there is provided a frequency meter 396 and the adjustment screw .388 which serves to move magnetic coil 385 angularly in the direction of the double arrow 390. In the event of frequency decrease this is equivalent to a decrease in the rotary speed of the disk 346 and therefore for decreased frequencies there will be a smaller angle between the mag: netic records on the disk 340 than for higher frequencies on the driving motor. By calibrating tnescale m .adjacent con m in terms of' motor 338, but usually qfdinary ggod commen .cial service sumces.

Thus, it win be observed that the .two anzu-- larly spaced magnetic records in passing under each pick-up coil cause a pair of flashes of the neon light 3,49 and that the two pairs of flashes may be moved with respect to eachother until the adjacent flashes off-the two pairs coincide. When this condition exists the angular spacing of the pick-up coils is the same asthe angular l smcing of the magnetic records.

Disfuncture.-The Disjuncture condition is essentially an apparatus testing arrangement by which errors may be eliminated. When a magnetic record passes under a pick-up coil, the nach is caused to occur in the neon light, as previously explained, but there is no way of telling whether the flash occurs when the pick-up of the magnetic record is under the center of the coil or whether it occurs 'when the record is displaced one way or the other from the center line of the coll. There are unavoidable physical variations between the two pick-up coils 318 and 385 and other variation -factors occur which are due to changes in temperature and operating conditions of thc various circuits and thermionic tubes. The Disjuncture circuit condition is provided as a test whether the magnetic records are in fact under the ,coils when the flashes occur. To carry out this operation the handle 1|3, Figure 15, is moved to the Disjuncture position which causes switches I-VI to be moved into the position shown in Figure 19 and switches VII-X are then magnetically actuated to the positions as also shown ir. Figure 19. Referring to Figure 13 it will be noted that when the movable contact of microswitch A is normally in contact with contact 555. a positive potential is impressed on contact 595 through resistance 691. This voltage is communicated through movable contact 695 of switch A to junction 104 and thence through resistor 15|A and condenser 102, in parallel, to ground terminal 103. This serves to charge condenser 102 to a.

| by way of microswitch B which is held in the l depressed condition during this operation. Therefore, the primaries 453 and 493 of transformers 454 and 494, respectively, are simultaneously energized, tubes 45| and 499 simultaneously become conductive and the double strength signal is transferred through the recti- 4 fier tube 418 from both anodes at the same time to junction 523 on the line D. The neon light 345 is flashed but this is incidental for the signal is also transferred by way of microswitch III and IV to both lines 530 and SI5 simultaneously and thence by way of microswitches VIII and IX, re-

spectively, to the No. 1 pick-up coll 318 and No. 2 pick-up coil 385 so as to energize both of the coils simultaneously. Hence, there is placed upon the magnetic ring 341 revolving disk 345, two zones of magnetization which are angularly displaced by an angle equal to the angle between the No. 1 pick-up coil and the No. 2 pick-up coil.

The operator control handle H3 is then movedto the Read position and the record is read. If everything is operating perfectly when such a record is played back, the neon light will show three dashes. Actually, if everything is right there are two pairs otilashes but adjacent flashes of the two pairs coincide so that the signal actually appears as three flashes of light angularly disposed, the two angles between adjacent flashes being equal to the angle between the two pick-up coils.

If the signal does not consist of three flashes, as above described, but instead shows two pairs with the middle two close but visibly displaced, some malfunctioning exists. This can usually be corrected by varying the gain and bias of amplifiers No. 1 or No. 2 or both. By so doing the adjacent flashes of the two pairs can be brought into juxtaposition. In this -manner the instrument is adjusted so that the angular position between the pick-up coils as read on the scale 342 will actually be the angular distance between the magnetic records on the revolving disk.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves t the specific embodiments herein except as defined by the appended claims.

What we claim is:

1. A timing apparatus for recording and indicating short time intervals comprising a record and indicating means including a circular member of magnetizable material and a quick responsive signal lamp both mounted for rotation in a circular path thereon, motor means for rotating the record and indicating means at a constant rate, a pair of electromagnetic elements movable relative to each other located adjacent the circular member in cooperative electromagnetic relationship, a pair of incoming signal carrying circuits, a pair of amplifier networks, one for each electromagnetic element and switch means responsive in one condition of operation to communicate incoming signals received on either incoming signal circuit to one of the electromagnetic elements to record on the magnetizable member signals received on either incoming signal circuit and responsive in another condition of operation to communicate signals generated by either electromagnetic element through its corresponding amplifler network to the quick responslve signal.

2. The apparatus of claim 1 further characterized in that in a third condition of operation of said switch means a testing signal charge is communicated simultaneously to both electromagnetic elements.

3. The apparatus of claim 1 further characterized in that the electromagnetic elements are movable relative to each other while maintained in cooperative relation to the magnetizable eloment.

4. The apparatus of claim 1 further characterized in that each amplifier network includes a thermionic amplifier tube and a gas-type trigger tube responsive thereto.

5. The apparatus of claim 1 further characterized in that each of said amplifier networks includes an extremely sensitive shielded section and said switch means is located partly in each shielded section and partly without, the switch means part without the shielded section being manually operable and the switch means part within the shielded section being magnetically operated responsive to the operation of the switch means part without said section.

HARRY WILLIAM HOFFMAN. GROVER H. HELMER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,365,470 Egerton Jan. 11, 1921 1,883,907 Hathaway Oct. 25, 1932 1,925,483 Dubois Sept. 5, 1933 2,011,366 Lord Aug. 13, 1935 2,012,170 Kayatt Aug. 20, 1935 2,091,357 Goldsmith Aug. 31, 1937 2,213,534 Rowe Sept. 3, 1940 2,229,451 Gulliksen Jan. 21, 1941 2,245,124 Bonn June 10, 1941 2,298,608 Bates Oct. 13, 1942 2,336,897 Shipton Dec. 14, 1943 2,370,133 Begun Feb. 27, 1945 2,370,134 Begun Feb. 27, 1945 2,370,166 Hoeven Feb. 27, 1945 2,370,176 Kornel Feb. 27, 1945 2,395,127 Kornei Feb. 19, 1946 FOREIGN PATENTS Number Country Date 317,477 Great Britain July 30, 1929

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