High security pay television system

Claim 2

A pay television broadcast system comprising a broadcast station including scrambling means for imposing a scrambling signal on the program signal, the scrambling signal being generated through use of the inverse of a signal generated from a pre-selected changeable system code; a plurality of receiving station decoders each including descrambling means for imposing a descrambling signal complementary to the scrambling signal on the received broadcast signal, the descrambling signal being generated from the same system code, each receiving station decoder including therein a fixed, station-unique internal code; and a removable digital memory module for each receiving station decoder, each module carrying thereon a fixed, station-unique external code which can be combined with the internal code of the proper receiving station to generate the system code in the receiving station, the memory module being removable from the receiving station and replaceable so that the system code can be periodically changed.

Claim 3

A pay television broadcast system as claimed in Claim 1 wherein the broadcast station further includes means for imbedding a broadcast code in the broadcast signal; wherein the receiving station decoder further includes demodulating means for recovering the broadcast code; and wherein the broadcast code is used by each receiving station, in addition to the internal code and the external code, to generate the system code.

Claim 4

A pay television broadcast system as claimed in Claim 2 wherein the receiving station is capable of writing a portion of the broadcast code onto the portable memory module so that the memory module can be later read at a remote location to determine the broadcasts viewed.

Claim 5

A pay television broadcast system as claimed in Claim 3 wherein the broadcast code includes a broadcast station identification code unique to the broadcast station so that the broadcast station code can be written onto the portable memory module so the broadcast station for any broadcast viewing can be determined.

Claim 6

A pay television broadcast system as claimed in Claim 2 wherein the broadcast code includes a program content identification code and wherein the receiving station includes a user-selectable content selection input so that the descrambling signal is not generated if the program content as indicated by the program content code has not been selected by the user-selected input.

Claim 7

A pay television broadcast system as claimed in Claim 2 wherein the memory module carries more than one external code and the particular external code to be used for any particular program is determined by a portion of the broadcast code.

Claim 8

A pay television broadcast system as claimed in Claim 1 wherein the descrambling signal is generated by multiplying the digits of the system code by a pre- selected system multiplicand to generate a numerical sequence and by then sequentially converting the numerical sequence to an analog signal by digital to analog conversion.

Claim 9

A pay television broadcast system as claimed in Claim 1 wherein the digital memory module is an electrically alterable read-only memory (EEPROM).

Claim 10

A pay television broadcast system as claimed in Claim 1 wherein the combination of the internal and external codes includes a simple addition of the two numerical codes.

Claim 11

10 . A pay television broadcast system as claimed in Claim 1 wherein the broadcast station further includes means for imbedding a broadcast code in the broadcast signal; wherein the receiving station decoder further includes demodulating means for recovering the broadcast code; and wherein the receiving station decoder further includes means for writing on the removable memory module so that at least a portion of the broadcast code can be written in the memory module to indicate the portions of the broadcast signal viewed.

Claim 12

In a pay television system, a receiving station signal decoder for a scrambled broadcast signal comprising an internal fixed memory containing a fixed, station-unique internal code; a removable, electrically alterable, removable memory module containing at least one pre-written station-unique, external code which can be combined with the internal code to generate a systemwide system code; means for generating a descrambling signal complementary to the scrambling signal upon input of a proper numerical sequence; and a microprocessor programmed (1) to read the internal code from the fixed memory and the external code from the protable memory module, (2) to combine on the external code with the internal code to generate the systemwide system code, and (3) to generate'and output to the descrambling signal generating means a numerical signal generated from the system code.

Claim 13

In a pay television system, a receiving station signal decoder for a scrambled broadcast signal comprising an internal fixed memory containing a fixed, station-unique internal code; a removable, electrically alterable, removable memory module containing at least one pre-written station-unique, external code which can be combined with the internal code to generate a systemwide system code; means for generating a descrambling signal complementary to the scrambling signal upon input of a proper numerical sequence; and a microprocessor programmed (1) to read the internal code from the fixed memory and the external code from the protable memory module, (2) to combine on the external code with the internal code to generate the systemwide system code, and (3) to generate'and output to the descrambling signal generating means a numerical signal generated from the system code.

Claim 14

A decoder as claimed in Claim 11 further including a demodulator to demodulate a numerical broadcast code imbedded in the broadcast signal and wherein at least a portion of the broadcast code is written onto the removable memory module so that the module can later be read at a remote location to determine broadcast viewing.

Claim 15

A decoder as claimed in Claim 12 wherein at least a portion of the broadcast code is also used by the microprocessor in conjunction with the internal and external codes to generate the system code.

Claim 16

A decoder as claimed in Claim 13 wherein there is more than one external code in the memory module and the particular external code to be used for a program is selected by a portion of the broadcast code.

Claim 17

A decoder as claimed in Claim 12 wherein at least a portion of the broadcast code contains a program content identification code and wherein there is a user-selectable content selection input to the decoder, the microprocessor further programmed to read the user-selectable input to not generate the system code if the program content code has not been selected by the user.

Claim 18

A decoder as claimed in Claim 15 wherein the user-selectable content selection input is selectably lockable.

Claim 19

A decoder as claimed in Claim 12 wherein the broadcast code contains both program_identification code and a broadcasting suction code and wherein both the program identification code and the broadcasting station code are written into the memory module so both the programs viewed and the particular broadcasting station can be later determined by reading information in the removable memory module.

Claim 20

A decoder as claimed in Claim 11 wherein the descrambling code generating means includes a digital to analog converter to convert the numerical output from the microprocessor to an analog descrambling signal.

Claim 21

A decoder as claimed in Claim 18 wherein the microprocessor is further programmed to multiply each digit of the system code times a pre-selected multiplicand to generate a numerical sequence to output to the digital to analog converter.

Claim 22

A decoder as claimed in Claim 11 wherein the combining of the external code with the internal code includes adding the two codes together.

Claim 23

A decoder as claimed in Claim 11 wherein to read the external code from the removable memory module the microprocessor must present a latch code to the removable memory module, the removable memory module being non- readable without presentation of the proper latch code.

Claim 24

The decoder as claimed in Claim 11 wherein the removable memory module is an electrically erasable programmable read only memory integrated circuit.

Claim 25

A pay television broadcast system comprising a broadcast station including (1) scrambling means for imposing a scrambling signal on the program signal to create a scrambled broadcast signal, the scrambling signal being the inverse of a signal generated from a pre-selected changeable code, and (2) an encoder to imbed a broadcast code in the broadcast signal; a portable, removable, reusable memory module for each viewing station carrying the changeable code thereon; and a receiving station decoder for each receiving station including (1) means for reading the changeable code. from a removable memory module inserted in the decoder, (2) means for imposing a descrambling signal complementary to the scrambling signal on the received broadcast signal, the descrambling signal being generated from the changeable code, and (3) writing means for writing at least a portion of the broadcast code on the memory module so that the memory module can later be read at a remote location to determine the broadcast segments viewed at the receiving station.

Claim 26

A pay television broadcast system comprising a broadcast station including (1) scrambling means for imposing a scrambling signal on the program signal to create a scrambled broadcast signal, the scrambling signal being the inverse of a signal generated from a pre-selected changeable code, and (2) an encoder to imbed a broadcast code in the broadcast signal; a portable, removable, reusable memory module for each viewing station carrying the changeable code thereon; and a receiving station decoder for each receiving station including (1) means for reading the changeable code. from a removable memory module inserted in the decoder, (2) means for imposing a descrambling signal complementary to the scrambling signal on the received broadcast signal, the descrambling signal being generated from the changeable code, and (3) writing means for writing at least a portion of the broadcast code on the memory module so that the memory module can later be read at a remote location to determine the broadcast segments viewed at the receiving station.

Claim 27

A pay television broadcast system as claimed in Claim 23 wherein the memory module is an electrically erasable programmable read only memory integrated circuit.

Claim 28

A pay television broadcast system as claimed in Claim 23 wherein the memory module carries more than one code thereon with the address of the code to be used being selected by the broadcast code.

Claim 29

A pay television broadcast system as claimed in Claim 23 wherein the writing means in the decoder writes a portion of the broadast code in the memory module during each pre-selected segment of broadcast programs so that viewers can be billed on the basis of program segments rather than whole programs.