US2053025A - Synchronizing system - Google Patents

Description

Sept l, 1935- G. L. ERICKSON' ET A1. 2,053,025

' SYNCHRONIZINGYSTEM l Filed May 21, 1934 2 SheeLZs-Sheel 1 l+ i l ,Pau/Z E. Tete? Y Ctttomeg el? (for/'actor -l Sept. 1, 1936. G. l.. ERICKSON ET A1. v 2,053,025

SYNGHRONIZING SYSTEM Filed May 2l., 1934 2 Sheets-Sheet 2 Relay I y Jnueniozg Geo/ge L. Encima/z .qll

Patented Sept. 1 1936 unirse sTArss PATEWq OFFHQ SYNCHRNEZING SYSTEM Application May 2i, 1934, serial No. 726,130 e claims. (ci. 17e-53) This invention relatesv to synchronous communication systems and is particularly adapted for high speed printing telegraph systems.

The main object o the invention is 'to accu- 5 rately maintain synchronism between the transmitting and'receivng apparatus by employing thermionic tubes in the control circuit of 'the driving fork or constant frequency source employed to drive the distributor and 'continuously l deriving from the received signal impulses correction components in either direction which are applied to the tubes, to thereby supply a correction component to the natural period of the driving fork.

15 In order to apply the correcting components to the control circuit, a relay, when operated by signaling impulses transmitted over the line, serves in conjunction with the correcting segments of the distributor to furnish a correcting impulse'` 2@ upon a storing condenser with every small departure from synchronism in either direction, and

vthese reversals are continuously averaged in a 35 Figures 5 and 6 are diagrams illustrating modiv iications of ourinvention.

Figure l illustrates a typical transient current reversal received at the end of a telegraph line. A polar relay connected to Ireceive the signal im- 40 pulses will operate its armature very nearly at the instant at which the current wave crosses the zero axis.

type are received over acircuit free from distortion or emraneous interference, the relay arma- ,.5 ture will operate at precisely the-same point on each current reversal as indicated in Fig. 1.

When the relay is connected to an actual circuit however, the received current impulse has '50 superposed upon it, various disturbances due to interference currents which distort the wave shape somewhat as indicated in Fig. 2. Due to this distortion, the current reversals in the signal im-Y pulses do not recur at the same uniform periods 56 and hence the operations of the relay armature oc- If successive current reversals of this cur at somewhat irregular intervals as indicated in Fig. 2.

We have shown in Fig. 3 a single current impulse such as received over -a circuit distorted by interference, and have indicated below the 5 irregular manner in which the relay armature operates when receiving distorted current waves of this type. The dotted curve passing through the distorted current wave indicates the transient that would be received if no interference wereA l0 present.

The corrector rings of the receiving distributor are shown in the lower part of the figure and as indicated, ii the speed of the receiving distributor is in enact synchronism with the received current impulse, the relay armature will operate at the instant the distributor brushfis crossing the insulation between two segments `and hence no correction would occur. I

Our correcting arrangement disclosedV herein 2g maintains synchronism between the receiving vdismantle and the sending distributor at distant points on a telegraph circuit by applying a correction component to the natural period of oscillation of a driving fork or constant frequency source used to drive the distributor, thereby causing the receiving distributor to operate exactly in phase with the sending distributor. The corrector brush indicated in Fig. 3 is connected in a correction circuit in the manner indicated in Fig. 4, which illustrates one embodiment of our in- The corrector rings and rotating brush b of the distributor operate in conjunction with the polar correcting relayCR which responds to the re- 35 ceived signals to deliver a small incremental pulse to a condenser C for every operation of the relay armature. The polarity of this incremental pulse will depend upon the particular corrector segment over which the brush happens to be passing at the instant the relay armature is operated. The alternate segments are marked F and S respectively to indicate the fast or slow correction component which is transmitted to the correction circuit. The operation of the relay armature due to current reversals which occur when the brush is passing over the fast segments F, result in negative polarity incremental pulses while those which occur when the brush is passing over slow segments S, result in positive incremental pulses. These short correcting pulses occur at the instant they relay armature is passing across the gap-from one contact to the other. y Y

'I'he incremental correctingimpulses are em- 55 ployed to charge the condenser C. In order that the condenser` may function as an accumulator to continually average the receivedincremerital charges-and exercise a constant governing action upon the amplifier tube or tubes of the correcting circuit, we lnterpose a neon tube NI between the condenser and the corrector segments. This completely isolates the condenser and thus conserves its charge during the interval between successive incremental pulses.

It is evident that when the condenser receives an equal number of positive and negative incremental pulses per unit of time, its potential will not change. When, however, a preponderance of positive or negative impulses is received, the'potential across the condenser is either addedto or subtracted from the normal grid biasing potential determined by the drop across the resistances R1 and R2.

It will be evident-that when the :relation'between the speed of the brush b and thev is passing over the segments marked F.' Consequently the grid side of the condenser C will become more positive,`thus reducing the eective grid bias potential on the tubes T, T' and causing the plate current to increase. The plate current of the amplier tubes flowing through the fork magnet M produces a damping effect upon -the driving fork F. This tends to reduce the frequency of the fork and hence slows the speed of the phonic motor PM which rotates the distributor brushes until synchronism is again established. Likewise if the speed of the brush b should tend to decrease with respect to the current reversals, a greater number of relay operations would occur when the bru'sh is passing over the segments marked F, thus impressing a preponderance of negative incremental pulses upon the grid side of the condenser and correspondingly reducing the plate current of the amplier tubes.- The effect of this, of course, is to reduce the damping eil'ect of the magnet FM, resulting in an increase in the fork frequency with a corresponding increase inspeed of the phonic motor.

Synchronism will beestablished at a point where the condenser receives just enough excess incremental charges of the proper polarity per uiit of time to maintain the plate current of the tubes at the proper value for exact synchronism of the sending and receiving distributors.

In the modification shown in Fig. 5 we have interposed'a transformerv TR between the corrector brush and the condenser. 'I'his arrangement possesses certain advantages under condi- -tions which require control of the size of the incremental pulses. In the arrangement illustrated in Fig. 4, the time duration of the pulse is-equal to that of the travel time of the relay armature; whereas in the arrangement shown in Fig. 2 the time duration of this incremental pulse can be controlled by varying the resistance and inductance in the transformer primary circuit.

One of the advantages derived from our method of correction is the remarkably small amount of shift En lthe relative position of the receiving distributm brush with relation to the incoming signals when operating near the limits of correction. Iii all correctingdevices a deiinite varialarities depending upon the forward or rearward tion in speed must occur in order to bring about a correction. In most correcting devices the correction eect is more or less momentary. This action introduces some phase shifting effect between the receiving distributor brush and the re- 5 ceived signals and consequently reduces the operating margin. In Vour 1correcting arrangement, however, we are able to maintain synchronism within fairly Wide limits with a small phase shifting eiect. Lilo yThe arrangement of our correcting circuit is/ such that the correcting effect is protected against sudden changes such as power induction surges. By employing the high insulation resistance of a neon lamp and the accumulator function of the condenser the grid bias is sustained at its proper value for a considerable length of time. The correcting brush will, therefore, assume and maintain an average midway position between the (F) fast and (S) slow correcting segments. The condenser works through a range approximately of about 25 volts positive to 10 volts negative and its potential is from 5 to 40 volts negative with respect to the cathode.

Unless the relation between the incremental pulses per unit of time and the capacity of the condenser is correct, there will be a tendency to hunting of the receiving distributor brush with respect to the received signal reversals. We have found that in order to prevent this hunting action, the eect on the potential'across the condenser (Ec) for succeeding incremental pulses of the same polarity should become less and less. This may be accomplished by employing a charging potential (V) which is comparable with the potential across the condenser-C. Then as the potential across the condenser becomes large, the magnitude of the-incremental charges is reduced, since the potential available to charge the condenser (V-Ec)..becomes less.

'Ihe general principles of our invention may be applied -to any driving mechanism which may have its speed corrected by inequality of the incremental pulses applied toa correcting circuit. Thus our corrector arrangement is also applicable to the control of the frequency of an electrical oscillating circuit or any periodic arrangement which is controllable by a direct current component from the plate circuit of our corrector through oneof the oscillator coils, thus changing its inductance sumciently to affect the period of oscillation of the oscillator.

1. A system-for correcting slight departures from synchronism between a rotary receiving ,device and incoming signal impulses, comprising an instrumentality responsive to the incoming signals operating in conjunction with said rotating device to produce incremental impulses oi' podeparture of said device from synchronism a capacity storing means for averaging the cremental impulses received over aytime in rval, means for insulating said storing means while permitting at all times the passage of said incremental impulses thereto, and means for utilizing the resulting charge stored during any interval to correct the speed of said rotary device when a slight departure in phase relation occurs.

2. A system for synchronizing an oscillatory fork with a series 'of received impulses, which comprises instrumentalities for- 'producing incremental correcting impulses of one polarity or the other depending upon the phase relation of 75 v 2,058,025 ,the fork oscillations and the received impulses, a

storing condenser for receiving said incremental impulses, means for insulating said condenser from said instrumentalities while permitting at all times the passage of said incremental impulses. whereby said incremental impulses produce over a time interval an average potential charge stored in said condenser, and means including correcting circuits for utilizing the resulting potential charge to correct any departure in phase relation between the oscillations of the fork and said received impulses.

3. A system for synchronizing an oscillation generator with incoming signal impulses, which comprises an instrumentality responsive to incoming signals operating in cooperation with mechanicallyv moving parts to produce incremental impulses of one or the other polarity depending upon the departure in phase relation between oscillations of said generator and said signal impulses,^a capacity storing elementnarranged to receive said incremental impulses, an ionizable gaseous medium insulating said storing element but permitting at all times the passage of said incremental impulses thereto and means including a correcting circuit for utilizing the resulting varying potentials of said element to vary the frequency ofthe oscillations of said generator in accordance with the frequency of the incoming signal impulses.

4. A system for correction of phase departure in synchronous apparatus, comprising a rotating recelving device, a relay responsive to incoming signal impulses to produce in conjunction with said 'rotating device during the travel interval of the relay armature, incremental impulses of one or the other polarity dependent upon the phase relation between the rotating device and the incoming signal vimpulses for any departure from synchronism, a capacity element for storing said incremental impulses,- an ionizable medium permitting at all times the passage of said incremental impulses, the resulting polarity charge upon said storing element operating to correct the speed of said rotating device when a slight departure in phase relation occurs.

GEORGE L. ERICKSON. PAUL E. TETER.

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