US2403561A - Multiplex control system - Google Patents

Description

July 9, 1946 J. P. SMITH 2,403,561

MULTIPLEX CONTROL SYSTEM Filed Nov, 28, 1942 .3 Sheets-Sheet l 1 7F44/ /V/r ,se

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MULTIPLEX CONTROL SYSTEM Filed Nov'. 28, 194224 3 Sheets-Shed'l 2 chilli/f5 BH @M Gttorneg July 9, 1946. J. P. SMITH MULTIPLEX CONTROL SYSTEM Filed Nov. 28, 1942 5 Sheets-Sheet 3 c//mwa "9,9

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John P. Smith, Granbury, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application November 2s, 1942, serial No. 467,227

l 11 Claims.

My invention relates to multiplex systems for controlling a plurality of channels or devices and particularly to systems wherein the control is effected by the transmission of a plurality of electrical pulses.

One object of the invention' is to provide an improved method of and means for controlling a plurality of signal channels or devices with the use of a single carrier frequency wave or single communication channel. Another object of the invention is to provide an improved method of and means for controlling with a, single Irequency carrier wave or single communication channel a plurality of signal channels or devices in any desired sequence or grouping. Another obj ect of the invention is to provide an improved control system wherein the desired control is eil'ected :by the coincidence of two or more pulses.

In practicing 'one-of the preferred embodiments of the invention, pulses are produced in periodically recurring groups with the individual pulses having a time spacing of a few microseconds, ten or .twenty microseconds, for example, and with the groups of pulses recurring at a suitable rate such as 30 groups per second. These groups of pulses are transmitted to a delay line in a receiver whereby the pulses are delayed diiferent amounts at a plurality of taps on the delay line.

Each channel or device to be controlled is connected to receive delayed pulses from one of said taps and is also connected to receive pulses from a point common to all channels. At the said common point the delay may be zero or it may The invention will be better understood from the following description taken in connection with the accompanying drawings in which Figurelisablockandcircuitdiagramofthe transmitter for one embodiment of theinvention,

FlgureZisablockandcircuitdiagramofa receiver for use with the transmitter of Fig. 1,

Figures3 to3c arefgraphsthatarereferred to in explainingl the operation of the system showninFigalandz,

Flgure4isablockandcircuitdiagramillus- 2 trating a variation of the invention shown in Figures 1 and 2,

Figure 5 is a eblock and circuit diagram of a receiver for use in another embodiment of my invention, and

Figures 6 and 6e are graphs which are referred to in explaining the operation of a system using the receiver of Fig. 5.

In Fig. 1, the transmitter comprises a pulse generator III which produces a pulse I recurring at a. certain rate such as 30 per second. 'Ihe pulse I is supplied to a delay line II which is terminated for non-reilection and which is tapped at a plurality of points to supply at successive points a pulse which is delayed an increased amount. The delayed pulses appearing at the several taps are supplied through switches I2, I3, I4 (and through other switches not shown) to amplifier tubes I6, I1 and I8, respectively, and to other ampliier tubes not shown. The undelayed pulse I is supplied to an amplifier tube I9. The outputs of all the amplier tubes I6, I'I, etc., are added by employing a plate resistor 2I common to the several tubes whereby a group of time spaced pulses I, 2, 3, 4, etc., is obtained. In this embodiment of the invention, the time spacing between the first pulse and the second pulse is one-half the time spacing between the remaining 'adjacent'pulsea In the example illustrated, the amplifier tubes I6, IT, etc., are connected to points on the delay line Il where the pulse is delayed 10, -30, microseconds, etc., thus giving a delay of 20 microseconds between al1 pulses except the iirst two which have onehalf this delay between them. It is evident that pulse I is always included in the transmitted group and that any other pulse or plurality of pulses may be transmitted or omitted by closing or opening the proper switches I2, I3, Il, etc. For example, in the drawings, the switch I2 is shown open whereby the pulse 2 of the group is omitted as indicated by the fact it is shown in dotted line.

Fig. 2 shows a receiver forcontrolling a plurality of channels in accordance with the inclusion or omission of particular pulses comprising the periodically recurring group of pulses transmitted by the apparatus of Fig. 1. The receiver includes a delay line 26 to which the periodically recurring groups of pulses are applied. The delay line 26 may be 'a duplicate of the line II of Fig. 1, having a non-reilecting termination and a plurality of taps along the line.

Tap No. I is connected to the control grid of an amplifier tube 21, which is one of a pair of 3 tubes controlling channel No. I. The other of these tubes, indicated at 28, has the undelayed received signal applied to its control grid. 'I'he tubes 21 and 28 have a common plate resistor 28 oi' high resistance, the plate end of which goes either positive or negative a maximum amount (depending upon the polarity of the received pulses) when pulses appear simultaneously on the grids oi tubes 21 and 28. Assuming that the received pulses are of negative polarity, maximum positive voltage appears at the plate end of resistor 29 when a pulse on the grid of tube 21 is coincident with a pulse on the grid of tube 28. This voltage may be applied over a conductor, indicated by the legend Channel No. I, to an amplifier tube 3| that is biased beyond platecurrent cut-off so that only said maximum positive voltage resulting from coincidence of two particular pulses will cause plate current flow in tube 3l for control or signalling purposes.

Similarly, taps No. 2, No. 3, etc., are connected to thegrids of vacuum tubes 32, 33, respectively, and to others not shown. The tubes 32 and 33 are associated with 'vacuum tubes 34 and 36, respectively, which have applied to their grids through the common conductor 35 the same undelayed signal that is applied tothe grid of tube 28. The pairs of tubes 32-34 and 33-35 have common plate resistors 31 and 38, respectively, the plate ends of which are connected to vacuum tubes 33 and 4I, respectively, through the conductors indicated by the legends Channel No. 2 and Channel No. 3. By using plate resistors 29, 31, etc., of high resistance and by applying a small amount of positive bias to the grids, the pulse output of a pair of tubes is of large amplitude when coincident pulses are applied to the grids. v

The operation of the system of Figs. 1 and 2 is shown more clearly by the graphs of Figs. 3 to 3c. Comparing the graphs of these iigures, it will be seen that of the pulses applied to the common conductor 35, the pulse 2 is coincident with the pulse I of the group appearing at tap No. I. Thus channel No Il is controlled by pulse 2; specifically, if pulse 2 is included in the transmitted group, 30 pulses per second will be produced in the plate circuit of tube 3l and these pulses may be utilized for any desired control or signal purpose. If the pulse 2 is omitted from the transmitted group by opening the switch I2, then no control will appear in the plate circuit of the tube 3 I since none of the remaining pulses is coincident with any pulse appearing at tap No. I. Similarly, a comparison of Figs. 3 and 3b and of Figs. 3 and 3c shows that pulse 3 controls channel No. 3 and that pulse 4 controls channel No. 4. Likewise, the pulses 5, 5 and 1 may be utilized to control additional channels, not shown. By employing this embodiment of the invention any channel or any number of channels can be controlled by means of pulses sent over a single communication channel such as a single carrier wave.

As illustrated in Fig. 4, a variation of the abovedescribed embodiment of the invention may be employed wherein the common conductor 35 is connected to the end of the delay line 26 rather than to the start of the line and wherein the niicrosecond delay occurs at the end of the line rather than at the start of the line. With this arrangement, all the transmitted pulses have the full-time or microsecond spacings except the last two pulses which have the one-half or 10 microsecond spacing. I'he operation is the sameas previously described. 'I'lie graphs of Figs. 3

4 to 3c illustrate the operation of Fig. 4 if it is assumed that the direction of their time axis is reversed, i. e., if it is assumed that time increases from right to left instead lof from left to right.

Fig. 5 illustrates a receiver for an embodiment of the invention wherein all pulses of a transmitted group have .the same time spacing. In this embodment, the control is sequential, i. e., any one of a plurality oi.' channels may be opened or closed although the flexibility offcontrol provided by the previously described embodiment is lacking. The evenly spaced pulses I, 2, 3, etc., may be produced at a transmitter similar to that shown inl Fig. 1. At the receiver they are impressed upon a delay line 5I having taps No. l. No. 2, etc., evenly spaced from the start of the line. Each tap supplies signal to one of a pair of tubes, the other`tube of each pair having undelayed signal applied thereto over a conductor 52. For example, tap No. I is connected to the grid of tube 53`while the conductor 52 is connected t0 the grid of the other tube 58 of the pair of tubes 53-54.

Just as described in connection with the receiver of Fig. 2, each pair of tubes such as the pair 53-54 supplies a control pulse to its particular control channel in response to the simultaneous application of pulses to the control grids of the two tubes. The sequential control is illustrated by the graphs in Figs. 6 to 6c. Comparing Figs. 6 and 6a, it will be seen that if pulses I and 6 are transmitted, the pulse I appearing at tap No. 5 will be coincident with the undelayed pulse 8 whereby channel No. 5A will be controlled. If only Ithese two pulses are transmitted, there will be no coincidence of pulses at any other channel.

To control any particular channel, pulse I is always transmitted together with one other pulse assigned to that particular channel. For example, comparing Figs. 6 and 6c, pulses I and 4 will be transmitted to control channel No. 3A and there will be no coincident pulses at the other,

channels. It will be noted that in this embodiment control of one channel (such as No. 5A) is released when pulses are transmitted to take over control of a diiferent channel (such as No. 3A). If this is an objectionable feature for certain applications of the invention, then the rst described embodiment of the invention should be employed.

I claim as my invention:

1. A multiplex system comprising means for producing a group of time spaced pulses, means for transmitting said group of pulses to a receiver which includes a delay line, means for supplying said group of pulses to said delay line whereby they are delayed as they travel along said line, a plurality of circuits each of which is responsive to a plurality of coincident pulses, each of said circuits being connected -to a different point along said delay line whereby each circuit receives said group of pulses delayed different amounts, means for also supplying said group of pulses to said circuits with the same amount of delay at each circuit, and means for including or omitting pulses from said transmitted group whereby pulse coincidence may be made to occur at the desired circuit at the receiver.

2. A multiplex system comprising means for producing periodically recurring groups of time spaced pulses, means for transmitting said groups of pulses to a receiver which includes a delay line, meansfor supplying said groups of pulses to said delay line whereby they are delayed as they of which is responsive to a pluralityof coincident pulses, each of said circuits being connected to a different point along said delay line whereby each circuit receives said groups of pulses delayed different amounts, means for also supplying said groups of pulses to said circuits with the same amount of delay at each circuit, and means for including 'or omitting pulses from said transmitted groups whereby pulse coincidence may b e made to occur at the desired circuit at the receiver.

3. The method oi controlling a plurality of circuits at a. remote point which comprises producing a group of time spaced pulses, transmitting said group of pulses to said remote point, delaying said group of pulses different amounts at said remote point to produce differently delayed groups of pulses, supplying to each of said circuits one of said delayed groups of pulses with the delay of said group different at each circuit, also supplying said group of pulses to said circuits with the same amount of delay at each circuit, and including or omitting pulses from said transmitted groups whereby pulse coincidence may be made to occur at the desired circuit at said remote point.

4. The method of controlling a plurality of circuits at a remote point which comprises produc-iy ing periodically recurring groups of time-spaced pulses, transmitting said groups of pulses to said remote point, delaying said groups at said remote point by different amounts equal to the time spacing of said pulses, supplying to each of-said circuits one of said delayed groups of pulses whereby each circuit receives said groups oi.' pulses delayed different amounts, also supplying said groups of pulses to said circuits with the same amount of delay at each circuit, and lncluding or omitting pulses from said transmitted groups whereby pulse coincidence may be made lto occur at the desired Acircuit at said remote point.

5. A multiplex system comprising means for producing a group of time spaced pulses, said group comprising a plurality of successively occurring pulses having similar time spacing and a pair of pulses that have a different time spacing, means for transmitting said group of pulses to a receiver which includes a delay line, a plurality of circuits each of which is responsive to a plurality of coincident pulses, certain of said circuits being connected to evenly time-spaced points along said delay line whereby each of said certain circuits receives said group of pulses delayed diiferent amounts, another of said circuits being connected to a point on said delay line where said group of pulses is delayed a diierent amount than said even time spacing, means for also supplying said group of pulses to said circuits with the same amount of delay at each circuit,

' and means for including or omitting pulses from said transmitted group whereby pulse coincidence-may be made to occur at the desired circuit at the receiver.

6. A multiplex system comprising means for producing a group oi time spaced pulses, said group comprising a plurality of successively occurring pulses having time spacing therebetween o! a certain value and a pairof pulses that have a time spacing of one-half said certain value, means for transmitting said group of pulses to a receiver which includes a delay line, a plurality of circuits each of which is responsive to a plurality ofcoincidentpulmcertainotsaidcircuitsbeing connected to evenly time-spaced points along said delay line with the time spacing equal to said certain value whereby each of said certain circuits receives said group oi pulses delayed different amounts, another of said circuits being connected to a point on said delay line where said group of pulses is delayed by an amount equal to one-half said hcertain value, means for also supplying said group of pulses to said circuits with the same amount of delay at each circuit whereby coincidence of certain pulses is obtained at certain 0i.' said circuits, and means for including or omitting pulses from said transmitted group whereby pulse coincidence may be made to occur at the desired circuit at the receiver.

7. A multiplex system comprising means for producing a group of time spaced pulses, said group comprising a plurality o'f successively occurring pulseshavingsimilartimespacingpreceded' by a pair of pulses that have a dierent time spacing, means for transmitting said group of pulses to a receiver which includes a delay line, a plurality of circuits each oi.' which is responsive to a plurality of coincident pulses, certain of said circuits being connected to points along said delay line where the delay between said points is the same as said similar time spacing whereby each of said certain circuits receives said group of pulses delayed diierent amounts, another of said circuits being connected to a point near the start of said delay line where said group of pulses is delayed by an amount equal to said diilerent time spacing, means for also supplying said group of pulses to said circuits with the same amount of delay at each circuit and with said same amount less than said dierent amount, and means for including or omitting pulses from said transmitted group whereby pulse coincidence may be made to occur at the desired circuit at the receiver.

8. The invention according to claim 7 wherein said diierent time spacing is equal to one-hall' said similar time spacing.

9. A multiplex system comprising means for producing a group of time spaced pulses, said group comprising a plurality of successively occurring pulses having similar time spacing followed by a pair of pulses that have a different time spacing, means for transmitting said group of pulses to a receiver which includes a delay line, a plurality of circuits each of which is responsive to a plurality of coincident pulses, certain of said circuits being connected to points along said delay line where the delay between said points is the same as said similar time spacing whereby each of said certain circuits receives said group of pulses delayed diiferent amounts, another of said circuits being connected to a point near the end of said delay line where said group of pulses is delayed by an additional amount equal to said diierent time spacing, means for also supplying said group oi.' pulses to said circuits after the pulses have passed through the delay line to a point beyond said last-mentioned point, and means for including or omitting pulses from said transmitted group whereby pulse coincidence may be made to occur at the desired circuit at the receiver.

10. The invention according to claim 9 wherein said different time spacing is equal to one-half said similar time spacing.

11.'A multiplex system comprising means for producing a group of time spaced pulses, said group comprising a plurality of sucosively occurling pulses having similartime spacing, means for transmitting said group of pulses to a.v receiver which includes a delay line, means for supplying Asaid group of pulses to said delay line whereby they are delayed as they travel along said line, a. plurality of circuits each of which is responsive to a plurality oi'. coincident pulses,

.said circuits being connected to points along said delay line where the delay vbetween said. points is the same as said similar time spacingl whereby lJorim P. sun'rn.

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