US2753393A - Television coding system - Google Patents

Description

July 3, 1956 M. G. PAWLEY ET AL 2,753,393

TELEVISION CODING SYSTEM Filed Aug. 51, 1951 2 Sheets-Sheet 1 INVENTOR$ @rwz afazrley JMZJZ. .'wizg.

JV W P A'TTORNEY y 1956 M. a. PAWLEY ET AL 4 2,753,393

TELEVISION CODING SYSTEM Filed Aug. 31, 1951 2 Sheets-Sheet 2 INVENTORS 1y raa ij az ley emZflu'aofig,

\ a ATTORNEY United States Patent TELEVISION CODING SYSTEM Myron G. Pawley, Alexandria, Va., and Jacob M. Sacks, Silver Spring, Md., assignors, by mesne assignments, of one-third to Lena Becker Paris, exeeutrix of Israel Richard Paris, deceased Application August 31, 1951, Serial No. 244,622

8 Claims. (Cl. 1785.1)

The present invention relates generally to coding systems and is more particularly concerned with coding systerns which are designed to vary periodically. The object of this invention is to provide such a system with simple and facile means for varying the code as desired.

The present invention is designed primarily for use and cooperation with subscribers television systems, such as the system shown in our co-pending application, Ser. No. 230,618, filed June 8, 1951, and the system shown therein is hereby embodied in the present application and is made a part hereof. In the system shown in this copending application, the televised image is coded at the broadcasting station and the code is varied periodically, as from day to day or from program to program. Each subscribers television set is provided with a corresponding code system which also needs to be pre-set in agreement with the code employed at the broadcasting station. For this purpose the coding unit at the subscribers receiver is provided with a group of two-position switches which need to be set in one position or the other in agreement with a key code which the subscriber has to obtain from the broadcasting station for each performance. The present invention aims to provide a ready means whereby the subscriber may set or adjust the group of switches so that the coding system generates the desired code.

In addition, the preesnt invention aims to render the coding system substantially tamper-proof. For these purposes the casing which houses the coding system is provided with a chamber having a slot-like opening or entrance and which is designed to receive a code card which will bear, by punchings or the like, the key code for the specific performance and for the specific receiver. Each of the group of switches which determine the code has an operator which projects into the chamber from one face thereof, thereby normally maintaining the switches in a predetermined position. By the insertion of the code card into the chamber some of the switches are moved from the normal position to the second position in accordance with the key code for the desired performance and for the specific receiver and thereby the coding system will be set to generate the desired code.

Another feature of the present invention is that means are provided which make it possible for the machine to identify or recognize a genuine code card and will cooperate only with such genuine cards. The means for accomplishing this end includes a first part which is disposed or fixed in the casing and a second part carried by the code card which renders the first part effective to energize the code system.

It is contemplated that the code cards of the present invention should be supplied to the subscriber for his future use and that these cards should be redeemable or exchangeable for other cards if the subscriber does not use the card. For this purpose, the chamber which receives a code card may be provided with means for mutilating the card or otherwise marking it to show that the card has been used and is not redeemable.

The organization and manner of operation in the present invention and further objects or advantages thereof will be best understood by reference to the following specification ad the accompanying drawings, it being understood that these serve to illustrate a preferred embodiment of the invention and that variations thereof falling within the scope of the appended claims will be apparent to persons skilled in the art.

Iln the drawings, some of which are on an enlarged sca e:

Fig. 1 is a perspective of the coding unit embodying the present invention;

Fig. 2 is a view of one face of the code card receiving chamber taken on line 22 of Fig. 1;

Fig. 3 is a view of the opposite face of the code card receiving chamber taken on line 3-3 of Fig. 1;

Fig. 4 is a view of one type of code card;

Fig. 5 is a wiring diagram of the identification system cooperating with the card shown in Fig. 4;

Fig. 6 is a view of another type of code card;

Fig. 7 is a sectional view taken on line 7-7 in a system employing the card of Fig. 6.

The housing 10 shown in Fig. 1 houses within it a coder unit or coding system of any suitable type such as the types shown and described in the above co-pending application. It is thought unnecessary to describe the coding system shown there for the manner in which the present invention cooperates with the coding system can be fully described without any discussion of the coding system itself.

The cable 13 and multi-contact plug 14 is employed for connecting the coding system housed in the housing 10 to the normal television receiving apparatus 19 which is provided with a plug receiving receptacle 15. When the plug 14 is inserted into the plug receiving receptacle 15 the electrical connections between the coding system in the housing 10 and the television receiver 19 are established as shown in the co-pending application. The switch 12 may connect a power source to the coding system.

The switches which need to be preset for each performance in accordance with a key code in order to adjust the coding system to generate the desired code are disposed in the housing or casing 10 and have their operating arms 21, which may be spring pressed, extend into the chamber 17. The code cards which are employed in the present system have two purposes which coperate to render the apparatus tamper-proof. One is that each card carries a key code for a specific performance and the other is that the card carries devices which cooperate with other fixed devices in the coder unit for introducing the delay line of the unit into the scanning system of the television receiver. This other phase of the invention serves as a means by which the machine recognizes the card as genuine and cooperates only with genuine cards.

The present application discloses two alternate systems for recognizing or identifying the card as genuine and which may be employed for switching the delay line of the coding system into the scanning circuit; as to other phases of the present invention, such as the key code on the code card and the manner in which the card cooperates with the arms 21 and presets the switches, they remain the same on both types of code cards.

We shall therefore here first describe the parts of the code box and chamber 17 and the code card which cooperate to preset the switches, it being understood that this phase of the invention is common to both forms of the invention.

The code card is designed to fit fairly snugly and to be forced into chamber 17 through its entrance 16. The

chamber and the card may preferably be keyed to each.

other so that the chamber will accept the card only when it is presented in the correct position, as by providing As shown, the code zone of the card may have code .punchings 24 which are designed to receive some of the switch operator arms 21 while the dotted and unpunched areas in the code zone serveto depress the corresponding switch operators. Thus bythe number and disposition of the code punchings '24 the desired switch arms are depressed and moved to their second position, while-the other arms enter the punchings and the switches remain in their normal biased position, in accordance with the key code for the performance.

As .another feature of the present invention, the code cards and the switch arms cooperate to prevent the cards from being withdrawn .once the card has been inserted for operation. For this purpose the operator heads 21 of the switches are wedge-shaped as shown at 25, these heads being spring pressed by springs 26 disposed in the switch casing 27 and against the collar 28. The upper sloping face of the head 21 permits the head to be pressed inwardly against the spring 26 as the card is inserted until the upper edge of the card is flush with the entrance 16. At this point some of the operator heads 21 enter the punching 24 and the lower faces of the heads 21 prevent the card from being retrieved. The leaf springs 30'may be carried by recesses in the face of the chamber 17 opposite the face carrying the switches, and press the code card yieldingly against the wall of the chamber and 'keep the card in operative position.

The card remains in the chamber throughout the coded program for which the key code on the card was particularly prepared. At the end of the program the subscriber turns off switch 12. The card may remain in the chamber until the user or subscriber later wishes to receive another coded performance for which he had previously obtained a code card. At this time the user inserts the new card against the previous card pushing the same edgewise. This pressure of the upper edges of the code punchings against the wedge shaped operator heads 21 will cause the same to be depressed against the action of the springs and permit the card to be pushed downward through the chamber 17 and into the receptacle 72 where these used cards may be permitted to accumulate. If desired, the receptacle may be locked against access by the subscriber and may be unlocked or unlatched by the service man when the coding system is subjected to periodic inspection, say once a'year. The service man then removes the cards. It may also be desirable to mutilate or otherwise mark the used cards to show clear evidence that it has been used. For this purpose, a scoring or rnutilatingdevice 32 may be mounted in the outlet 33 of the chamber 17 so that as the used card is being forced downward out of the chamber 17 it is being scored or otherwise marked or mutilated.

The mutilating device is particularly desirable for the purpose of readily distinguishing a used from an unused card, when and if the receptacle is made accessible to the user.

The mutilating device is preferably so disposed that it scores or mutilates the portion of the card which bears the identification element as the cell or diffraction grating morefully described below. An identification device as the replica difiraction grating would be mutilated so that it becomes useless.

If desired, latching pins operating in the manner described may be provided independently of the switches and the code cards are then provided with suitable openings to'receive such latch pins. The switch arms may then have conventional rounded operating heads.

By means of the system as thus far described the subscriber may obtain from the telecasting station a group of code cards for a group of programs in the immediate future; The subscriber is free to use the cards or not or to use only a selected number of such cards. He may then return the unused cards and be credited with V 4 them or exchange them for other cards. The invention as thus far described is applicable to both types of code cards and to both types of identification systems.

In the system, to which the present invention is particularly applicable, the delay line and other parts of the coding system are interposed between the horizontal synchronizing generator and the horizontal scanning generator which are conventional components of television receivers. When the receiver is employed for receiving uncoded'programs these two components are connected directly to each other and the coding system is by-passed. Before a coded program can be received this connection needs to be opened and the delay line and electronic switch interposed.

To accomplish these ends the present invention provides circuit means for operating switches which normally by-pass the coding system and establish a direct connection between the horizontal synchronizing pulse generator and the scanning generator but which operate when the card is inserted into the'chamber to interpose the delay line and the electronic switch.

Broadly stated, the means for accomplishing this switching operation includes two cooperating parts. One part is fixed'and disposed in the coding unit casing and the other part is carried by the code card. Two forms of this invention are shown herein. One such system is illustrated in Fig. 4 and Fig. 5 and the other system is shown in'Figs. 6 and 7. In both forms the switch operating system cooperates with the coding system as thus far described to render the present coding system tamper-proof so that subscribers cannot tamper with the coding system so as to 'renderthe same available to them without the use of code cards.-

' system carried by the code card. The'remainder of the switching system is mounted in the code casing and is by itself inoperative to effect the desired switching.

As will be observed from Fig. 5, the cell or cells 35 serve to supply positive voltage to the grid 37 of the triode 38 which is normally biased to cut-off. The application of the positive voltage from the cell 35 renders the triode' 38 conductive and the relay 39 is energized thereby operating the switch 40 to open its normally closed back contact and to close the normally open front contact." Thisserves to insert the delay line into the circuit between the horizontal synchronizing pulse generator and the'scanning' generator and the coding system becomes effective.

The inner wall of the chamber 17 is provided with a resilient termnal41 which contacts the positive face of the cell and the opposed face of the chamber carries a similar contact 42 for grounding the negative terminal of the cell. v

In the system as thus far described the cell serves as an identification for the card to the machine and the coding unit will refuse to operate if a card is inserted which it does not recognize as genuine.

Figs. 6 and 7 show another identification system for switching the coding system into the television receiver employing another identification device. In this system electro-optical devices are employed for energizing the relay 39 to operate the switch 40 as previously described. An optical device necessary to render the electro-optical system operative is carried by the code card. The electrooptical system comprises a source of light and a photoelectric cell. When the photocell 51 receives light the current in the cell is amplified by the amplifier 52 and the relay 39 is energized to operate the switch 40 to insert the delay line in the television receiver between horizontal synchronizing pulse generator and the scanof light and the photocell are such that normally, that is without the code card and its identification device in the chamber 17 no light reaches the photocell. The code card carries for its identification device a light refracting element 63 which serves to direct the light to the photocell and thereby the circuit means including the relay 39 is energized and the switch is operated or moved to its second position and maintained in this position during the program or as long as switch 12 is closed and the card remains in the chamber 17. Many types of refracting elements may be employed. In the preferred form a replica diffraction grating 63 is employed to direct a beam of light upon the slit 54 in front of the photocell 51. The replica diffraction grating 63 may be in the form of a separate element that is inserted in a suitable opening in the card or it may be aflixed to one face of the card or the transparent card material itself may bear the grating as shown in Fig. 6. The source of light is preferably monochromatic in the form of a slit 55. The collimator lens 56 directs parallel light rays upon and through the grating and the lens 58 serves to focus or image the light issued from the grating 63 upon the slit S4 and the photocell 51. In the absence of the grating the light will be concentrated on the line 60 on the axis of the lens 58. With the grating a sharp line of light will fall on the slit 54. The distance from the slit S4 to the line 60 is determined by the number of lines per inch in the grating or by the grating space. Thus the apparatus can be designed to be effective only wtih a grating having a grating space falling within narrow limits.

The particular value of the use of the diffraction grating lies in that the subscriber will find it virtually impossible to duplicate it.

When the subscriber wishes to receive a coded program, he inserts the code card into the chamber 17. Because of the bead 70 and groove 11 the card can be inserted only when held in its correct position. As the card is inserted some of the switch heads will enter the punchings in the code zone. When the upper edge of the card is approximately flush with the entrance 16 the switch operating heads will be selectively depressed or permitted to enter the punchings. These operator heads or, if desired, latches provided exclusively for this purpose, will hold the card in position so that it cannot be withdrawn. The card energizes the circuit means for operating the switch 40 to insert the code system into the television set and at the same time the nature of the code generated by the code system is established by the cooperation between the operating heads 21 and the code punchings.

With switch 12 in the oif position no power is available to any of the devices in the coder unit and as a consequence the switch 40 is in its biased position and in contact with its back contact. In this position the delay line is by-passed and the television receiver is available for receiving uncoded conventional signals and is operable in its normal or conventional manner. For receiving coded signals the subscriber, in addition to inserting the code card, also operates the switch 12 to its on position. This supplies power to all the devices in the casing 10. The relay 39 thereby becomes energized by virtue of the presence of the code card in the chamber 17 and by the switch 12 in the closed position.

Thus this arrangement permits the normal operation of the receiver 19 even when the code card is in the chamber 17 provided the power switch 12 is open.

In the absence of the cell or the replica difiraction grating or some similar device carried by the card designed to cooperate with other parts in the casing for rendering the coding unit effective, a subscriber may after obtaining a code card from the telecaster, duplicate the card and use the duplicate for receiving the coded program and return the original unmarked or unmutilated for credit. The present invention makes this method of bootlegging very difficult.

By means of the present invention, tamper-proof subscribers television systems may be had in which the business relationship between the telecaster and the subscriber are relatively simple.

Having described the invention we do not wish to be limited to the embodiments thereof described and claim as our invention the following:

1. In combination, a housing having a first chamber, a second chamber and an opening for access to the second chamber, a switch disposed in the first chamber biased to one position, and means for moving said switch to a second position comprising a first part fixed in said housing and a second part carried by a card insertable into said second chamber, said first part comprising a normally ineffective photoelectric system, and the second part comprising an optical device for rendering the system eifective.

2. The combination of claim 1 in which the first part comprises a source of light and a photoelectric cell and the second part comprises a device for directing the light to the cell.

3. The combination of claim 2 in which the second part is a diflraction grating.

4. In combination, a television receiver, a coding unit connected therewith, and a code setting and control systern for said coding unit for enabling intelligible reception of a subscription television program having a coded unintelligible component, said code setting and control system comprising a sealed housing, a master switch wholly contained in said housing and inaccessible from the outside thereof for rendering the coding unit selectively operative and inoperative, said housing having a slot opening therein, a plurality of code switch operators accessible in said slot, a key code card adapted for reception in said slot and to activate selected code switch operators, said card having authenticating means embedded thereon, sensing means in said slot for detecting the presence of said authenticating means, and means responsive to said sensing means upon detection of said authenticating means to operate said master switch for rendering said code unit operative.

5. The combination set forth in claim 4, wherein said sensing means comprises a photoelectric system, and said authenticating means comprises a light modifying means.

6. The combination set forth in claim 4, wherein said sensing means comprises a light source and photoelectric cell, and said authenticating means comprises a means for altering the path of light from said light source.

7. The combination set forth in claim 4, wherein said authenticating means comprises a voltage source.

8. The combination set forth in claim 4, wherein said sensing means includes a means responsive to applied voltage, and said authenticating means comprises a means for altering the voltage applied to said sensing means.

References Cited in the file of this patent UNITED STATES PATENTS 2,251,525 Rosenthal Aug. 5, 1941 2,488,207 Lea Nov. 15, 1949 2,501,274 Hamilton Mar. 21, 1950 2,561,752 Perdijon July 24, 1951

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