US2237533A - Secrecy and motor control device - Google Patents

Description

April 8, 1941.

. A. SPENCER SECRECY AND MOTOR CONTROL DEVICE Filed Nov. 23, 1938 2 Sheets-Sheet l p 8, 1941' J. A. SPENCER A 2.237.533

SEGRECY AND MOTOR CONTROL DEVICE F1 led Nov. 23, 1938 2 Sheets-Sheet 2 Riff/Vii INVENTOR h JZH. JP/VC 1? BY v I MWL/ ATTORNEY Patented Apr. 8, 1941 2,237,533 SECRECY AND MOTOR CONTROL DEVICE James A. Spencer, Teaneck, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application November 23, 1938, Serial No. 241,942

14 Claims.

This invention relates to telegraph systems either wire or radio. Telegraph messages when radiated into the air in accordance with the code sent out by an automatic transmitting head can be picked up by a receiver and interpreted by any one familiar with the code. In wire telegraphy messages likewise can be surreptitiously received and interpreted by tapping the wire over which the message is sent. It is therefore desirable to break up the message into unintelligible combinations so that unauthorized persons cannot interpret the messages,

It is an object of this invention to so change the communication signals sent over the air, or a conducting wire, that the message is unintelligible until it is transformed back into its original condition.

More specifically, it is an object of the invention to periodically reverse in accordance with a predetermined plan, the signal currents being transmitted and-received.

Other objects will appear in the following description, reference being had to the drawings, in which:

Fig. 1 is a diagrammatic illustration of the transmitting circuit.

Fig. 2 is a diagrammatic illustration of the receiving circuit.

Fig. 3 shows graphs of the signals in my improved system.

Referring to Fig. 1, CR indicates generally a series of relays arranged to operate in succession to serve as a counting device for reversing the transmitted current after a predetermined time. I indicates the transmitting relay operated by the automatic transmitter diagrammatically indicated at 2. This automatic tape transmitter is operated at a given constant speed to alternately elevate two plungers against a tape. having a series of spaced holes previously punched in accordance with the message that is to be transmitted. Since this type of tape transmitter is well known in the art the action is simulated in the diagrammatic illustration by a pivoted lever 3 moving about its center point to alternately engage contacts 8 and 5., whenever the perforations in the tape permit the contact to be made.

The relay I is polarized so that current through coil 5 and 1 moves the tongue in opposite directions to open and close the switch.

The switch tongue in relay 9 in one position engages the positive terminal l0 and in the other position the negative terminal ll. Relay 9 is a modified Gulstad relay that differs from the standard Gulstad relay chiefly in having a holding coil l2 that prevents the tongue l3 from vibrating at keying frequency while it is energized. When the coil i2 is deenergized the tongue l3 can then move in response to the impulses of coils l3 and I4. I

Current for the coils l3 and I4 is supplied from the contacts 10 and II through conductor I5. The coils are grounded at 16.

Reference character I! indicates generally a frequency control relay that is also of the Gulstad typeexcept that additional coils l8 supplied from the transmitting relay 1 correct the relay for any minute variation in frequency and phase by pulling the switch tongue into step with the impulses sent out by the transmitting relay l. The method of operation of the relay I1 is as follows:

With the switch tongue 49 in engagement with the positivemarking contact 20, current passes through conductor 2| to coil 22 through a suitable resistance 23, coil 24, to ground and back to the mid terminal of the battery 26. At the same time current from conductor 2i passes through coil 21 to the condenser 28, resistance 29, to ground and to the intermediate terminal of the battery 26. The coils 22 and 21 act in opposition at this time so that while coil 22 tends to force the switch tongue away from contact 20, coil 21 tends to hold it against the contact 20. The magnetic pull of coil 21 predominates at first because of the rush of current through condenser- 28. This charging current,'of course. diminishes with time while the current through coil 22 builds up with time because of the inductance in the circuit. When the current through coil 21 stops or is sufficiently reduced, coil 22 predominates and pulls the switch tongue l9 towards contact 25. As soon as the switch tongue leaves contact 20 the circuit is interrupted and the condenser 28 instantly discharges through coil 21 in the reverse direction passing also through coil 22 and the resistances 23 and 29. This flow of current, it will be noted, is in the direction to move the switch tongue [9 over against the contact 25 which it engages before the current dies down.

The currents through coils 22 and 21 are reversed when contact is made with terminal 25 because this is the negative terminal of the battery. With this reverse of current, coil 21 holds the tongue ill in engagement with terminal 25 while the condenser 28 is charging, and coil 22 attempts to open the contact but at first coil 21 predominates. When the condenser 28 is charged or reaches a certain stage of charge, the repelthe marking contact 3|.

lent force of coil 22 predominates and the switch tongue I9 is thrust toward the contact 29 and this action is aided, as before, by the discharge current of the condenser through the coils.

The relay i'l thus oscillates a:- a predetermined frequency depending upon the capacity of the condenser, the inductance of the coils, the value of the resistances and the potential of the battery. By proper; adjustment any desired frequency of vibration may be produced. This will be practically constant though there would be a tendency to vary slightly in frequency or in phase. The coil i8, however, will delay or speed up the action suificiently to hold the relay in step with the keying speed of the automatic tape transmitter 2.

The relay 9 also is adjusted so that it tends to oscillate in step with the keying speed of the transmitter 2 in exactly the same way as relay l1 but the tongue can move only when coil i2 is deenergized. This is deenergized only at the end of the operation of the bank of timing or countmarking and spacing contacts 3| and 32. These contacts each alternatelyv energize one-half of the bank of timing or counting coils CR in succession, one-half through conductor 33 and the other through conductor 34. The transmitter relays are not polarized so the reversed and unreversed current operate the coils in the same way. The operation of the transmitting system will now be explained.

It will be assumed that tongue I3 is in engagement with contact 10 when key lever 3 engages contact 4. Switch 3513 closed at this time and coil l2 energized. This puts positive current through coil 3 which throws the transmitting relay tongue 35 into engagement with the positive contact 31. This will send out a pulse in accordance with the signal through'the transmitting apparatus indicated by the tone keyer 33 and radio transmiter 33. This is marking current as tongue I! is in engagement with the marking contact 20.

When the lever 3 of tape transmitter 2 ena es contact 5 the polarized relay tongue 36 will be thrown against the blank contact 40 and no current will be sent out through the radio transmitter. Positive pulses are thus being used by the tape transmitter for marking and negative for spacing, but this is reversed periodically by the counting relays CR, the operation of which will now be referred to in detail.

As soon as the marking contact was made with contact 20. as first referred to, coil 24 of relay I! threw switch tongue 30 into engagement with Current from contact H) of relay 9 and conductor 4| then passed through switch contact 3| to conductor 33, conductor 42, coil 43 of relay I, conductor 44 and back-switch 44 of relay VIII to ground. Relay I was thus energized when the first marking contact was made in relay IT. The operation of relay I closes switch 45 and coil II is energized when the relay tongue swings on to spacing contact 32. This energization is produced by current flowing through conductor 34, the coil. Of

relay II, switch 45, conductor 44 and switch 44' to ground. Relay II operates and closes switch 41.

It should be explained at this time that relays I and II, as well as each of the other counting relays, are held energized by holding coils, the circuit of which is closed at 49 by the operation of. a preceding relay.

It will not be necessaiy to trace the circuit of the remaining coils of the counting relays as it will be seen that these relays are energized progressively by the vibrating tongue 30 and switches 41, 50, 60,13, H and 18.

The energizing and holding currents oi. the timing relays pass through the contact 44'. Therefore, when relay VIII is energized the circuits of all the timing relays are open by operation of this switch. This at once deenergizes all of them and this immediately reclcses switches 35 and 44'. The time taken to energize the series 01' relays may be made anything desired. While the series of relays RC were being energized the transmitter was sending out positive current for marking.

Just as soon as switch 35 opens, coil [2 is deenergized momentarily and this happens while the switch tongue 30 is starting towards space contact 32. Therefore, switch tongue i3, being new free to move, swings into engagement with its spacing contact I i. However, switch tongue I3 is forced to remain against contact II by the immediate re-energization of coil l2 by reclosure of switch 35.

The timing relays I to VIII are again energized progressively and during this period negative current is sent into the coils 8 and 1 of transmitting relay I. This means. of course, that the current will be reversed in these coils. Whenever a marking pulse is sent out by the tape transmitter 2 the relay tongue 33 will be thrown against dead contact 43 and when a spacing pulse is sent out relay tongue 35 will be thrown against the marking contact 31. This sends current to the antenna for the spaces of the signal.

In the embodiment shown the reversal of mark and space indications takes place every four dotcycles and the effect is shown in Fig. 3 where graph A represents a normal signal for the word "and." Graph B represents the same signal sent out by my improvement. with reversals taking place every four dot cycles. From a to b unreversed signals are transmitted. From I) to c the signals are reversed. At the point e the signals are again normal and so on. The signal radiated by the antenna is indicated by graph C.

"The receiver of Fig. 2 is arranged with a series of counting relays CR. a frequency control relay II, a transfer relay 9 and line relay generally indicated at 3|, that are the same or practically the same as the similar relays'in the transmitting end of the system.

The vibrations of the relay I1 are maintained in exact phase and synchronism with the transmitter by the pulses received through the receiving apparatus 32, 33, line 84, condenser 35 to coil l3. The switch tongue of the transfer relay 9 is prevented from continually oscillating by the holding coil i2 energized through back contacts 44 of the relay VIII. Parts in the receiving circuit of Fig. 2 that are similar to those of the transmitting system of Fig. 1 have in general similar reference characters.

In the receiving circuit, the polarized line relay consists of coils 33 and 33 which when energized move the switch tongue in opposite directions. Coil 88 predominates over coil 89.

When the rectified signal D is received, the current pulses passing over line 84 will cause switch tongue 9% to engage contact 9|. At this time tongue I3 is held against the positive contact and positive current will traverse coil 92 of the polarized recorder. Stylus 94 will be attracted toward coil 92. The moving tape 95 will then receive a mark" record. .then no current is being received over line 84 in the spaces of the signal the battery coil 89 throws the switch tongue 90 into engagement with contact 95. This energizes coil 93 which attracts stylus 94 into its spacing position. The recorder will record the signal at this time as given between the points a and b of graph E. 1

When reversed signals between D and c of graph D are being received over line 84, switch tongue 90 will be moved against contact SI for the spaces. At the point b of graph D the counting or timing relays CR have just completed their operation and the momentary interruption of current through coil [2 by the opening of switch 44' permitted tongue I3 to move against the negative terminal where it was held by the immediate re-energization of this coil. Therefore, at point b negative current commences to operate the recorder. This current passes from contact 9i through coil 92. The stylus is thrown away from the coil since the current is now reversed. A space will thus beformed. When the current ceases to flow in the line 84 at the termination or" the space. coil 89 throws the tongue against contact 95. This puts negative current through coil 93 and stylus 94 is repelled toward coil 92. This produces a "mark" record. Thus, the signals reversed at the transmitter are again reversed at the recorder and normal signals are produced as in graph E.

When the transmission of signals is interrupted for a substantial length of time there will be no current at the receiving end in coil 18 of relay I! to cause the timing relays to operate in exact phase and synchronism with the timing relays at the transmitter. To prevent the transmitting and receiving relays from getting out of step during interruptions, I provide slow release relays 97 which will not operate during the short spacing intervals between the code characters but which will operate when the transmission and reception ceases. When the slow release relays operate, the circuits of the locking coils l2 and the holding coils of the counting relays are opened by de-energization of coils 98. While the transfer relay and the counting relays at the transmitter and receiver still vibrate, the counting relays are inoperative until signal current again energizes the slow release relays. When this happens the coils l8 pull the receiving relays 9 and i! into step with the transmitting relays. The counting relays at the transmitter and receiver thus start in synchronism.

While I have described my invention in connectlon with a simplex system, it will be apparent t that it can be used equally as well in multiplex systems. for example, such as shown in Mathes Patent No. 1,979,484, November 6, 1934, and when so used the relays l1 and 19 can be used to control the distributors. as they are vibrating in synchronism and phase with the keying speed.

I have shown eight timing relays but any number from two on up may be used equally as well. Various other modifications may be used without departing from the spirit of the invention.

, Having described my invention, what I claim is:

1. In a secrecy telegraph system, means for making mark and space indications for transmitting a message and means for automatically interchanging the mark and space indications at predetermined intervals.

2. In a secrecy telegraph system, means for making mark indications by current of one character and a space by current of another character and means to automatically interchange the application of said currents for interchanging the mark and space indications.

3. In a secrecy telegraph system, means for making mark and space indications by pulses of different signs and means for reversing the sign of said pulses for automatically interchanging the mark and space indications after predetermined intervals.

4. In a secrecy telegraph system, for reception of signals having mark and space indications periodically interchanged, means for receiving the indications and means for automatically interchanging the mark and space indications at said predetermined intervals.

5. In a secrecy telegraph system, a transmitter switch, means to operate said switch for sending current of one character for marking indications, and a timing mechanism acting at predetermined intervals for automatically causing said means to operate said switch for sending current of the same character for space indications.

6. In a secrecy telegraph system, a source of current supply, a polar switch having mark and space positions, two coils for operating said switch, a keying device for sending current through one of said coils for moving the switch to one position and through the other for moving it to the other position, and timing means acting at predetermined intervals for alternately connecting said keying device to the positive and negative terminals of said supply.

7. In a secrecy telegraph system, a sending station, a code transmitter at said station for making mark and space indications, means at said station for automatically interchanging the mark and space indications of the code transmitter at predetermined intervals, a receiving station and means at the receiving station for automatically interchanging the mark and space indications in synchronism with the first mentioned means.

8. In a secrecy telegraph system, a sending station, a code transmitter at said station for making mark and space indications, means at said station for automatically interchanging the mark and 'space indications of the code transmitter at predetermined intervals, a receiving station, a recorder at-the receiving station and means at the receiving station for automatically causing the recorder to interchange the mark and space indications in synchronism with the changes made by the first mentioned means.

9. In a secrecy telegraph system, a sending station, a code transmitter at said station for making mark and space indications, a timing mechanism at said station for automatically interchanging the mark and space indications of -the code transmitter at predetermined intervals,

a receiving station, timing mechanism at the receiving station for automatically interchanging the mark and space indications in syn- 10. In a secrecy telegraph system, a sending station, a code transmitter at said station for making current variations indicating marks and spaces, a receiving station, means at the sending station for automatically interchanging the current variations to send space variations for marks and mark variations for spaces and means at the receiving station for automatically altering'the' recording means to thereupon record marks for spaces and spaces for marks.

'11; In a secrecy telegraph system, a polar relay for making mark and space indications, a source of voltage, a reversing switch, a code transmitter for applying energizing voltage to said relay from said source through said switch, a vibrator operating at constant frequency applying force tending to cause the switch to operate at a constant frequency, means for preventing the vibrator from operating said switch and means operating at predetermined intervals for neutralizing the action of the first mentioned means to permit the vibrator to operate the reversing switch.

12. In a secrecy telegraph system. a polar relay for making mark and space indications, a source of voltage, a reversing switch, a code transmitter for applying energizing voltage to said relay from said source through said switch, a vibrator operating at constant frequency applying 13. In a secrecy telegraph system for reception of signals having marks and spaces periodically interchanged at the transmitter, a receiver. electromagnetic means connected to the receiver for making alternate mark and space indications when voltage of one sign is applied thereto and for reversing said indications when voltage of opposite sign is applied thereto, a reversing switch, a source of voltage supply connected to said means through said switch and means for operating said reversing switch when the marks and spaces in the receiver are reversed.

14. In a secrecy telegraph system, a polar relay for making mark and space indications, a source oi voltage, a reversing switch, a transmitter for applying energizing voltage to said relay from said source through. said reversing switch, a vibrator operating at a constant frequency tending to cause said switch to reverse at said frequency the operating voltage applied to the relay, .a magnet when energized preventing said vibrator from operating said switch and means operating at predetermined intervals for tie-energizing said magnet for a half cycle of the frequency of said vibrator to permit it to operate said reversing switch, a recorder having electromagnetic means for making marks and spaces when voltage of one sign is applied thereto and for reversing the marks and spaces when voltage of opposite sign is applied thereto and means at the receiver for reversing the voltage applied to the electromagnetic means when the reversing switch at the transmitter is operated.

J AIVIES A. SPENCER.

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