US2576137A - Electrical switching system - Google Patents

Description

Nov. 27, 1951 J, NEwlTT 2,576,137

ELECTRICAL SWITCHING SYSTEM Filed July 2, 1945 2 SHEETS--SHEET 2 FREQ Sol/RC5 er/V, N

I IY/TZ'l/ING CONTROL VOL 7' 4655 INVENTOR. JOHN H, NfiV/TT A T T OIPNFV type or} electronic switcfies, th sjwitch'i' IIT eS C PS 9 o. H t when theswltol gglso set'yes es a detector totrps- 1232cradio fiequency ifito'audio frequency curme m oi art improved electronic switch 4 fi -Q y, M y detector arid electronic switch embodying my .o h rnectedto the oppositeends of'theprimary l u of Patented Nov. 27, 1951 ELETIiIbALSWIT-CHIN ramn:fiatici mdatclairma et-a1 Telephone and 1 In certain types otysw itchs' siic hl as .f Pli i e b "l r' T w t hin stem i which he switchingxcontrol; yoltages introduce Iliad" toit he accompanying dz awing s in; which Fig.- 1 is a schematic'and blook diagram of en electronic switching system e mbodying my invention utilizing a. gusty-pull arran emen 2 nd. 31 s simi a dia ram *Qf o ifi push-pull arrangements embodying my -invenqm ndl. V is 1 Si lar d a am; Q1=.. m e W12 invention.

5 will therefore -be"'180 tout *ofl phase with'ach The anodes ofjtriodes ,4 and'5 are connwt u an o m r I yliowh e, cQnd y; 12 is flqn c d. to. th 1 m 3 w th t mi n f; t

Pr mar be emeptes y aleaqo au the dsbiibed is a, push-pull amplifier.

I volt- H Lanfefielct in tlie output w ich .is

I T electronic switch I L we is q nneet i tur ugha es p f iiad a 30 25' o h midmim it 1 I te 'l o l me 3 fi d of whi h e o t fl a e m3%1?d. t ift es ids Qqe 11s \5,- ille e st woe ,e a .lsfl.; a is.reeter; re t n g=val e f hen he impedance iiut e ese ontlafyfi of ran o me s I, so nh th u o treq ency olta e v rom the 5 1111 2- wi ll not be shorted in saigi res istance. It will f thusbe'seengthatthe control voltages from source 22 are appliedto thegrids in'phase-as contrasted with the signal yoltages derived from the audio frequencysource 2;which latter-are appliedi180 T'out'of phase" tothegap with respect 13018301101116!- Accordingly -1t"wi;11 be se'enithat the efiect of the switching. "control voltages derived from the source 2 2 has opposed efiectg'fimthe'primary l0, of output transformer! l zso that any voltages "produced: by said risour'ce 22" :i'nrthe 'primaryr "I 0 -would buck each qtherwm and-produce no'cllrrent ;flo w whioh would affect the load. v It is-; preferred that the ;source 212 r'provide 60 'W hi ont ol y l e w h are ne tiv Q wi h PQfiv ns 11. 34 1 fi fi u ql fi .wwmwe e me t t e u n a- 186s, he m ts sixhe m a u lei t lu Y lI Qk"9d y y iqn 9il i fl-fan s""'ni;y be in thYbfmbiaftiaLin 4 The arm 35 which makes contact with any selected point on resistor 34 is connected by means of a coupling condenser 36 to the load, the other part of the load 3, the other side of the input to the load, being taken from ground as indicated by line 31. By moving arm 35, the relative gain or output derived from triodes 4 and 5 may,be varied. Thus the-gainof tubes 4 and i n nni orm cause a d tu are In said copending, application there is described a rectangular wave generator whose output is fed into a D.-C. rein sertion circuit so that the maximum positive level of the rectangular wavepulses is zero D'JC;

potential with respect to groundwhile the nega-Q- v tive pulses are substantially negative with respect to ground. Other arrangements may" likewise be employed for this purposetriodes 4 and 5 are normally biased to cut-off, that is, in theabsence of negative switching volt- .ages from source 22, no plate current flows'in the output of said triodes exceptwhen the positivev halves of signal energy are'impressed on the grids thereof. Thus the D.'-C. level between switching voltages is zero at the output of the triodes. When the negative voltages from the switching control source 22 are applied to the grids of triodes 4 and"5, they render said grids further negative and no plate current appears in the output of said triodes. Thus it will be seen that under all conditions of switching, no change in the D.-C. level of the'output' of the triodes is' produced and therefore no effect due to the switching'voltages appears in 'saidoutput. The foregoing operation plus the bucking effect of the switching voltages in the primary ll), of output transformer ll, doubly insure that the switching voltages do not cause impulses in the output. This is particularly necessary when 'the rate of repetition Off the switching voltages is at audio'frequency: f

Another arrangement for controlling triodes 4 and 5 when they-are dissimilar and to balance them is illustrated in Fig. 2; "In this embodiment, the cathodes of triodes 4 and 5 are connected to opposite ends of the resistor of a potentiometer 29, whose arm is connected to a movable arm 30, adapted to'connect to-any selected-point on resistor I]. It will be seen that by adjusting arm 30, the total bias voltage applied to both cathodes will be determined and by adjusting .the arm of potentiometer 29 the bias applied to one of the triodes may be increased while that applied to the other triode may be decreased. Thus if the two triodes are dissimilar, they can be properly balanced to cut-off. Arm 30 and the potentiometer arm are connected to ground through a by-passcondenser 3|.

In Fig. 3, the triodes 4 and 5 are illustrated as being in a cathode-follower type of push-pull arrangement, with the anodes of the triodes 4 and. 5 being connected to a positive source of anode potential, the negative source thereof being connected to ground. Biasing voltages for the triodes are derived from cathode resistors in- I cluding the resistor of the potentiometer 29 which is connected at its opposite ends to the cathodes of triodes 4 and 5, the arm of potentiometer 29 being connected inseries with a variable resistor '32 to ground, said variable resistor 32 being shunted by a by-pass condenser 33 to ground. An additional cathode resistor 34 is provided in shunt'with the resistor of potentiometer 29, resistor 34 serving as a'load resistor.

Since similar, by adjusting arm 35, the output derived from the triodes 4 and 5 will be balanced.

In Fig. 4 there is illustrated a single tube arrangement including a triode 38 which is used -.to detect energy from a radio frequency source 39 and is likewise used as part of an electronic switch, generally designated by the numeral 40, to switch the radio frequency energy, in translated form, with respect to the load 3. The radio frequency source 39 may be coupled to the triode 38 by means of a radio frequency transformer 4| whose primary is connected to theoutput of source 39 and whose secondary hasone end thereof connected to the grid of triode 3B, the other end 42 of the secondary being connected through a resistor 43' shunted by a radio'frequency by-pass condenser 44' to ground. The negative switching voltages from source 22 are applied at the end 42 of the secondary of transformer 4|. Triode 38 should be carefully biased to cut-off. For this purpose the arm l8"which is connected to the cathode of triode 38 is adjusted in relation toresistor ll of the voltage divider 15. The anode of triode 38 is connected of anode potential source I4 with a by-pass condenser 45 connected between said positive side and ground, and the radio frequency output being taken off with'respect-to ground through a coupling condenser 41 which is' connected to the load, the other part of the-input of the'load being from ground. Since triode 38 is biased to cut-off, the switching'voltages will produce no effect in the output thereof as has been explained hereinabove in connection with the arrangement of Fig. 1. Since, however, there is no bucking arrangement, as illustrated in Fig. '1, for cancelling the eifects of switching voltages, the

' adjustment of the bias should becarefully made in the arrangement of Fig. 4.

While I have described other details of embodiments of myinvention, it will be apparent to those versed in the art that numerous, changes in these details may be made without departing from the teachings of my invention. For example, while I have described the useof triodes and the application of both the switching voltages and the signal voltages between the grid and cathode of said triodes, it will be readilyapparent to those versed in the art that other multi-electrode tubes -may be used in place thereof with, for example, the signal voltages applied to one control electrode and the switching voltagesapplied to another control electrode. Various different types of input systems could readily be used in place of those hereinbefore described, asfor example, the .useof a phase inverter and aresistance coupling for the input to the push-pull arrangement. Accordingly, while I have described above the principles of my invention in connection with specific apparatusand particular modifications thereof, it to-be clearly understood that this description is made only by way of example I claim:

1. An electronic switching system comprising a pair of electron discharge devices each including an anode, cathode and control electrode, means for coupling said devices in a push-pull cathode-follower arrangement with the signal voltages being impressed on the control electrodes of said devices 180 out of phase with respect to each other, a source of switching voltages, means for impressing said switching voltages cophasally between the control electrodes of each of said devices and ground to control the conduction thereof, a resistor coupled at the opposite ends thereof to said cathodes, and means for coupling any one of a number of points on said resistor to said load, a second resistor coupled in parallel with said first named resistor, a parallel resistance capacitance network, means for adjustably connecting one end of said network to said second resistor, and means coupling the other end of said network to ground.

2-. An electronic switching system for switching signal voltages from a source to a load comprising a pair of electron discharge devices, each including an anode, cathode and control electrode, means coupling said devices in push-pull with the signal voltages being impressed on the control electrodes 180 out of phase with each other, a source of switching voltages, means for impressing said switching voltages between each of said control electrodes and ground substantially in phase and an output circuit comprising an output transformer, means for coupling the anodes of said devices to opposite ends of the primary of said transformer, and means for connecting the midpoint of said primary to a positive pole of a potential source, the secondary of said transformer being coupled to a load, a resistor interconnecting said cathodes, an adjustable parallel resistance capacitance network adjustably coupled at one end to said resistor and connected at the other end to ground.

3. An electronic switching system for switching signal voltages from a source to a load comprising a pair of electron discharge devices, each including an anode, cathode and control electrode, means coupling said devices in push-pull with the signal voltages being impressed on the control electrodes out of phase with each other, a source of switching voltages, means for impressing said switching voltages between each of said control electrodes and ground substantially in phase, means for biasing said devices to cutolT comprising a voltage divider connected across a source of potential and having one end grounded, a resistor, the opposite ends of which are connected to the cathodes, and a shorting member for connecting a selected one of a number of points on said resistor to a selected one of a number of points on said voltage divider, and a capacitor connected between said member and ground.

4. An electronic switching system comprising a pair of electron discharge devices each including an anode, cathode, and control electrode, means for coupling said devices in a push-pull arrangement with the signal voltages being impressed on the control electrodes of said devices 180 out of phase with each other, means for biasing said devices to cut-off so that only positive portions of the applied signal appear in the output of said devices, a source of negative switching voltages of such value as to completely block conduction of said devices, and means for impressing said switching voltages cophasally on the control electrodes of said devices.

JOHN H. NEWITT.

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

UNITED STATES PATENTS April 1941 An Electronic Switch and Square Wave Oscillator, by Cosby et al., pages 187-190,

Certificate of Correction Patent No. 2,576,137

THOMAS F. MURPHY,

Assistant ammim'oner of Patenta.

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