Pay per view television control device

A method and apparatus for providing access to an electrically controlled service for perdetermined periods of time employs a dual magnetically striped record medium encoded in a CRB format with data indicative of the periods of time during which access is to be provided. The data is read by a reader and stored in a processor having an internal clock and a comparator for comparing the instantaneous time output of the clock with the predetermined time period data encoded on the record medium for enabling a security device only when the instantaneous time is within the predetermined time period.

BACKGROUND OF THE INVENTION 
The present invention relates to apparatus for limiting access to an 
electrically controlled service to authorized users of the service. More 
specifically, the present invention concerns apparatus for enabling a 
security device which, when disabled, prevents unauthorized persons from 
gaining access to a service which is readily available to the user but for 
the impedance of the security device. The invention has numerous 
applications, as will subsequently be shown, one of which is in 
controlling access by television viewers to subscription television 
services. 
Community antenna television (CATV) enables subscribers to receive an 
enhanced signal carrying television programs broadcast on standard 
television channels, typically over cables connected to viewers' 
receivers, for improved program reception. As an adjunct to the broadcast 
for publically available programming, CATV operators have offered pay TV 
services wherein subscribers are supplied with additional channels of TV 
programming, not publicly available, in return for payment of a fee which, 
depending on the nature of the subscription service, may be a periodic 
fee, e.g. monthly, or a single usage fee which entitles the viewer to 
television viewing of a specific channel of programming during a 
preselected time period. CATV services may include the provision of 
several channels of television viewing which may be individually or 
collectively made available to subscribers. For example, one channel of 
television viewing may include first run movies or live theater plays; 
another may provide sports events; while still another channel may provide 
a schedule of television programs not available on the public access 
channels. 
In order to limit viewing of special programs to paying subscribers, it is 
necessary to be able to selectively enable and disable the apparatus which 
provides to each subscriber's television receiver, a signal suitable for 
viewing. As this cannot be feasibly done by having a technician from the 
CATV operator visit the subscriber's home before and after each program is 
viewed to perform the enabling and disabling operation, since it would be 
extremely costly, other methods of restricting access to TV programs are 
necessary. One approach to overcoming the need to send a technician to a 
subscriber's home is to enable and disable the subscriber's access to 
programming by remote control through the transmission of enabling and 
disabling signals to each subscriber's residence by complex transmitters 
and receivers and intermediary connecting lines. The apparatus required to 
accomplish remote control is complex and expensive and can only be 
feasibly used where there are a large number of subscribers among whom the 
cost of the equipment can be amortized over a period of time. The initial 
startup costs for assembling such a system and the uncertainty of the 
number of subscribers who can be expected to participate has discouraged 
smaller CATV operators from providing single program viewing services. 
Examples of systems which require the transmission of data from the CATV 
operator to the subscriber's television receiver are found in the U.S. 
Pat. No. 3,890,461 to Vogelman for a Ticket Operated Subscription 
Television Receiver and U.S. Pat. No. 4,058,830 to Guinet, et al for One 
Way Data Transmission System. The systems described in the foregoing 
patents rely on comparison between the transmitted data and data on a card 
furnished to the television subscriber. 
It is also known that a magnetically encoded ticket or record medium can be 
used to actuate a switching device for energizing an electrical mechanism 
such as an electrically operated gate for permitting access to building or 
a depository in a bank. Such tickets, however, do not lend themselves to 
use for limited subscription television viewing since they can be re-used 
indefinitely and, hence, once supplied to a subscriber provide no way of 
limiting the time during which TV access permitted by the ticket or record 
medium can be obtained. One attempt to remedy this problem is disclosed in 
the aforementioned Vogelman patent which discloses the destruction of the 
information on the data ticket by destroying the ticket with a motor 
operated device. 
It is also known in the art to employ a magnetic stripe to actuate a 
security device for enabling television viewing. Such a device is 
disclosed in U.S. Pat. No. 4,012,583 to Kramer for a pay TV control system 
which discloses a motel room key having a magnetizable stripe which 
permits a guest of the motel to gain access to television programs for 
viewing on a television receiver in his room. However, no information is 
encoded on the magnetizable stripe of the key in the Kramer patent so that 
the time of viewing or channels to be viewed cannot be selectively 
controlled. 
Thus, while it is seen that the prior art includes devices for or adaptable 
to gaining access to subscription television services, those which can 
economically be provided only at a subscriber's television receiver are 
very limited as to flexibility in controlling time and channel access, 
while systems which permit greater flexibility are complex and expensive 
and require transmission of special information from the television 
broadcasting head end to subscribers in addition to the television viewing 
signals. 
SUMMARY OF THE INVENTION 
The instant invention overcomes the aforementioned problems of the prior 
art in teaching the construction of and method of operating apparatus for 
providing access to an electrically controlled service for predetermined 
periods of time including a record medium adapted to have encoded on it 
data indicative of a definite time period during which access to the 
service is to be permitted and one or more sub-periods within a time 
period which sub-periods can be coextensive with or of shorter duration 
than the time period, a reader adapted to receive the record medium and 
store the data encoded thereon, a processor including a clock circuit 
having an output signal indicative of instantaneous time, including date, 
hour, minute and second, and a comparator for comparing the data stored in 
the reader with the clock output signal, and a security device operable in 
at least two states, one of which permits access to the service and the 
other of which prevents access to the service, the security device being 
responsive to the comparator for permitting and preventing access to the 
service as a function of the data encoded on the record medium and the 
instant time signal output of the clock. The invention provides for a dual 
head reader for reading data encoded on a data card, having parallel 
magnetic stripes, by the complementary return to bias method. The 
processor which compares the data encoded on the magnetic stripes with 
data generated by the internal clock controls a plurality of channels of 
programming each of which can function in a plurality of programming 
modes. Means for erasing the data encoded on the magnetic stripes after 
the data is read and stored is also provided. The apparatus of the 
invention can be employed in conjunction with numerous types of security 
devices. 
It is therefore an object of the invention to provide access to an 
electrically controlled service through the use of a disposable card 
having data encoded thereon which can be furnished to a subscriber in 
return for advance payment. 
Another object of the invention is to provide selective access to an 
electrically controlled service for predetermined periods of time without 
necessity for gaining access to the appliance which renders the service. 
Still another object of the invention is to provide access to an 
electrically controlled service by means of an apparatus which is 
compatible with numerous types of available and future security devices. 
A further object of the invention is to provide selective access to an 
electrically controlled service for a continuous predetermined period of 
time. 
Still a further object of the invention is to provide selective access to 
an electrically controlled service during predetermined discrete 
sub-periods of time within an overall time period. 
An additional object of the invention is to provide access to an 
electrically controlled service for a predetermined time duration 
immediately upon application of a data card to a card reader at the 
location of the service rendering appliance. 
Other and further objects of the invention will be apparent from the 
following drawings and description of a preferred embodiment of the 
invention in which like reference numerals are used to designate like 
parts in the various views.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, there is shown in FIG. 1 a functional block 
diagram of the apparatus of the preferred embodiment of the invention. The 
apparatus includes a reader 1 with magnetic reading heads 2a and 2b which 
are mounted on the card reader assembly 1. The magnetic read heads 2a and 
2b can be similar to those employed in conventional tape cassette readers 
the construction of which will be known to those skilled in the art. The 
card reader assembly 4 includes a top plate 6 and a bottom plate 8 which 
are mutually connected in parallel spaced relationship by spacer posts 10 
to form a channel having a cross section congruent to the cross section of 
the card 12, therebetween for slidably receiving a data card 12 
longitudinally inserted into the channel while preventing rotation or 
skewing of the card 12. On the data card 12 there are coded two parallel 
spaced magnetic stripes 14a and 14b having axes parallel to the axis of 
the channel along which the card 12 is translated as it is inserted into 
the reader 1, which are adapted to have encoded thereon, data specifying 
the channels of service to be offered to the subscriber and the times 
during which access to the service on each channel is to be provided. 
Mounted on the upper plate 6 adjacent and in longitudinal alignment with 
the data reading heads 2a and 2b is a magnetic erase head 16. The magnetic 
erase head 16 is energized to erase the data encoded on the card 12 only 
after the data has been read as will be described. 
In order to sense the presence of a magnetically striped data card 12 in 
the card reader assembly a conventional mechanical switch 18 has an 
actuator arm 20 disposed in the channel of the card reader 1 for receiving 
the data card 12. Insertion of the data card 12 into the card reader 1 
causes the switch 20 to pivot rearwardly thereby causing the normally open 
switch 18 contacts to close. 
Referring additionally to FIG. 3 of the drawings, it is seen that the 
magnetic reading heads 2a and 2b include inductive coils which are 
respectively connected to the inputs of amplifiers 22a and 22b. Filtering 
of noise and other unwanted signals appearing at the outputs of the coil 
2a and 2b is provided by capacitors 24a and 24b respectively. Each of the 
amplifiers 22a and 22b is provided with a respective feedback loop having 
a resistor 26a and 26b respectively. 
A 5 volt bias voltage is applied to the positive input of amplifier 22a 
through a voltage divider circuit including resistor 28a and resistor 30a. 
Similarly a 5 volt bias signal is applied to the positive input of 
amplifier 22b through a voltage divider circuit including a resistor 28b 
and a resistor 30b. 
The output of the amplifier 22a is applied to the input of a Schmitt 
trigger 32a. Similarly the output of amplifier 22b is applied to the input 
of a Schmitt trigger 32b. Bias voltage is applied to the Schmitt trigger 
circuits 32a and 32b by means of a common voltage divider circuit 
including resistors 34 and 36 and respective input resistors 38a and 38b 
which are connected to the respective positive inputs of the Schmitt 
trigger circuits 32a and 32b respectively. 
The two magnetic stripes of the data card 12 are encoded in accordance with 
the complementary return to bias (CRB) method. Complementary return to 
bias is a two track technique which has heretofore been used in 
applications which permitted the low density bit rates and wide band width 
attending the method but has not been used for selective access to 
services which are electrically controlled and, in particular, to 
subscription television services. In CRB encoding, each data cell on the 
record medium is set to one of four states. In the first state which 
represents a no data condition, both tracks are at magnetic south. In the 
second state which represents a zero, the first track is at magnetic south 
and the second track is at magnetic north. In the third state which 
represents a binary one, the first track is at magnetic north and the 
second track is at magnetic south. The fourth state wherein both tracks 
are at magnetic north can be used as an end of byte or other framing 
signal to separate data words. Because of the inherent inefficiency of CRB 
due to low density bit rates, CRB has been believed, until now, to be 
unsuitable for use in subscription television service applications. In 
addition the art has avoided CRB due to the necessity for wide band widths 
which are believed to increase vulnerability to noise and the 
susceptibility of the two track technique to skewing problems. However, 
CRB utilizes a reasonably simple logic network and has been found within 
the teachings of the invention, to be both a cost effective and highly 
reliable method of encoding data cards for subscription television use as 
employed in conjunction with the apparatus of the invention. 
The magnetic impulses recorded on the dual stripes 14a and 14b of the data 
card 12 induce voltage pulses at the outputs of the read coils 2a and 2b 
which are amplified by the feedback amplifiers 22a and 22b. The irregular 
pulse signal outputs of the amplifiers 22a and 22b are converted to square 
wave pulses by the Schmitt triggers 32a and 32b respectively and then 
applied to a central processor 40. 
As can be seen with reference to FIG. 3 the switch 18 is connected at one 
end to ground and at the other to a resistor 42 and parallel with input 
terminal 44 of a processor logic circuit in the central processor 40. The 
opposite end of the resistor 42 is connected to a 5 volt power supply. 
When the switch 20 is open, that is when there is no data card 12 in the 
card reader, the 5 volt signal appears at the input terminal 44 of the 
processor circuit 46 thereby indicating that there is no data card in the 
reader. When the data card 12 is inserted in the reader 1, the switch arm 
18 is pushed rearwardly thereby closing the switch 20 and bringing the 
input terminal 44 of the logic circuit 46 to ground potential thereby 
signalling the presence of the data card 12 in the card reader 1. 
When it is desired to erase the data encoded on the magnetic stripes 14a 
and 14b of the data card 12, in order to prevent reuse of the card, an 
erase signal appears at output terminal 48 of the logic circuit 46. The 
positive signal at the output terminal 48 is applied to the base of a 
transistor 50 through base resistor 52. The positive signal at the base of 
the transistor 50 turns the transistor on thereby permitting current to 
flow from the 5 volt power supply through the collector to emitter 
junction of the transistor 50 and then to ground through the erase head 
16. A single erase head 16 can be provided spanning both of the magnetic 
stripes or separate respective heads can be provided for erasing the data 
encoded on the dual magnetic stripes 14a and 14b. The data square wave 
pulse outputs of the Schmitt triggers 32a and 32b are applied to input 
terminals 58 of the processor circuit 46 to indicate whether proper AC 
power is being supplied to the system. A backup rechargeable battery is 
provided to provide sufficient power to run the system in the event there 
is an AC power failure. Upon indication from the signal applied to 
terminal 58 of the processor 46 that there has been an interruption in the 
AC power, the processor circuit 46 causes the backup battery voltage to be 
applied to power the apparatus. The battery power is supplied to the 
processor circuit 46 at input terminals 60, 62 and 64. In addition to its 
backup function, the battery provides the 5 volt bias used in the system 
as previously described. 
A 32 kHz oscillator 64 provides timing signals to the processor circuit 46 
through resistors 66 and 68. Undesirable harmonics from the oscillator are 
shunted to ground through capacitors 71 and 73, capacitor 73 preferably 
being a variable capacitor for precise tuning. 
The processor circuit 46, which can be a National Semi-Conductor integrated 
circuit COP420C, includes a clock network 47 which employs a frequency 
divider 49 and counter circuit 51 in cooperation with the oscillator 64, 
for generating instantaneous time signals indicative of the date, day, 
hour, minute and second, in a manner known to those skilled in the art. 
Input terminals 70,72 and 74 are provided on the processor circuit 46 for 
receiving clock setting signals which can be applied to the processor 
circuit 46 for initially setting the clock network 47 therein to the 
current data and time. The setting of the clock network 47 in the 
processor 46 is preferably done by the manufacturer or distributor of the 
apparatus before delivery to the consumer for installation on a television 
receiver. Instead of applying the clock setting signals directly to the 
processor circuit 46, clock setting signals can be encoded on a magnetic 
card and read by the card reader 1. An output signal from the card reader 
responsive to the clock setting signals encoded on the magnetic card can 
be applied to the processor circuit 46 to set the clock network of the 
processor 46 to the appropriate date and time. 
Upon insertion of the data card 12 into the reader, the data on the card is 
read and analyzed by the processor circuit 46 which includes a CRB decoder 
55. If the data is of proper format and deemed valid, a signal appears at 
output terminal 78 of the processor circuit 46 to energize a light 
emitting diode 80 thereby causing the diode 80 to light and indicate that 
the data card 12 has been accepted. In the absence of valid data, there is 
no change in the state of the output 78 and the light emitting diode 80 
remains extinguished. 
Clock data developed in the processor 46 is applied to the input of a time 
display module 82 which includes the decoding and driving circuitry for a 
digital time display 83 which displays the instantaneous time. An output 
signal appearing at terminal 84 of the processor circuit 46 enables the 
time display module 82 to receive the instantaneous time data from the 
clock network 47 in the processor 46. Only when the clock data is valid 
does the enable signal appear at the output terminal 84 of the processor 
circuit 46. The clock data itself appears at output terminal 86 of the 
processor circuit 46 and is applied to a respective input of the time 
display module 82. Output terminal 88 of the processor circuit 46 is also 
connected to the time display module 82 for setting the initial time for 
display and feeding data to the time display module 82. The time display 
module 82 decodes the incoming data from the clock 47 and provides 
appropriate output signals for digital display. The time display module 82 
is a component known to the art and can be an integrated circuit having 
the manufacturer's designation NSM4000A. 
The apparatus of the preferred embodiment of the invention is capable of 
activating up to three channels of programs in one of three modes of 
operation or a combination of modes. The channel or channels to be 
activated are defined by the data encoded on the data card 12 as are the 
time periods during which the data card 12 is valid and the sub-periods, 
within the time periods in which the data card 12 is valid during which 
viewing on each of the channels is to be permitted. A sub-period can 
encompass the entire time period during which the data card 12 is valid, 
or can be a shorter period of time included in the time period during 
which the data card 12 is valid. 
There are three modes of operation of the apparatus of the preferred 
embodiment of the invention. These modes of operation which have 
application in controlling access to subscription television services are 
conveniently designated pay per month, pay per view and wild card. In pay 
per month operation data encoded on the dual magnetic strips of the data 
card 12 designate one or more of the three channels and one month in which 
the data card 12 is valid. Upon acceptance of the data on the card 12 by 
the reader, the LED 80 is energized and lighted and the erase signal 
appears at the output terminal 48 of the processor circuit 46 for enabling 
the erase head 16 to erase the data encoded on the data card 12. When the 
data card is completely removed from the reader, the removal of the card 
is sensed by the switch 18 and the processor circuit 46 determines whether 
to enable the channel or channels designated in the encoded data for 
television reception. The data encoded on the card which is indicative of 
the month in which the card is valid is compared by a comparator 53 with 
data generated by the clock network 47 internal to the processor 46 and, 
as long as there is a correspondence between the two wherein the 
instantaneous time recorded by the clock 47 is within the month during 
which the card is valid, the channel or channels designated in the encoded 
card data are enabled. 
When a channel is enabled, an enable signal appears at a respective channel 
enable output terminal of the processor circuit 46 and an enable LED 
indicator signal also appears at a corresponding output of the processor 
circuit 46. Hence when the first of three channels of the preferred 
embodiment of the invention is enabled, an enable signal appears at output 
terminal 90 of the processor circuit 46 and an LED energizing signal 
appears at output terminal 92 of the processor 46 to cause light emitting 
diode 94 to light. Similarly, when the second channel is enabled, an 
enabling signal appears at output terminal 96 to light the diode 98. When 
the third channel is enabled an enabling signal appears at processor 
output terminal 100 and a light emitting diode energizing signal appears 
at processor output terminal 102 to energize and light a corresponding 
light emitting diode 104. 
Output terminals 90, 93 and 100 of the processor circuit 46 are each 
connected to a respective security device known to those skilled in the 
art for enabling or disabling television reception on the respective 
channel or for providing access to another electrically controlled 
service. 
A switching circuit for controlling a security device suitable for use in 
subscription television systems which employ either an interference 
carrier security device 141 or an outdoor negative trap security device 
143 is shown in FIG. 5. An enable signal from one of the outputs 90, 93 
and 100 of the processor circuit 46 is applied to the base of a transistor 
110 of a switching circuit through voltage divider action by resistors 112 
and 114. The enable signal is simultaneously applied through resistor 116 
to the base of a transistor 118, the emitter and base of which are biased 
by a 9 volt DC voltage applied through resistors 120 and 122 respectively. 
DC bias is also applied through resistor 124 to the collector of 
transistor 110 which is in turn connected to a diode 126 and resistor 128 
to the base of a transistor 130. High frequency suppression of output 
signals at the collector of the transistor 110 is provided by a grounded 
capacitor 132 connected between the diode 126 and resistor 128. The 
emitter of transistor 130 is connected to ground through resistor 134. 
The collectors of the transistors 118 and 130 are adapted to be connected 
to the security device 141 or 143 through a resistor 136. 
When an enable signal is applied to the previously described switching 
circuit, a filter can be permitted to remove an interference carrier 
signal or prevent the signal blocking action of an outdoor negative trap. 
The enable signal can also be used to activate and deactivate other known 
switching circuits compatible with security devices presently known to the 
art including those used with synch suppression, STV (secure television) 
and MDS (multidistribution service). 
A second mode of operation if the invention in a subscription TV 
environment is termed pay per view operation. In pay per view operation, 
the data encoded on the dual magnetic stripes 14a and 14b of the data card 
12 can specify one, two, three or four time periods within the month in 
which the data card is valid. The time periods are specified both as to 
the specific time of the month they are initiated and by their respective 
durations which can be from one half hour to sixteen hours, each, in the 
preferred embodiment. The comparator 53 of the processor circuit 46 then 
compares the instant time data output of the clock 47 in the processor 
circuit 46 with the data encoded on the data card 12 indicative of the 
time period during which pay per view operation is to be enabled. Upon 
acceptance of the data card 12 by the reader, the LED 80 lights and the 
erase circuit is enabled to erase the data encoded on the data card 12 to 
prevent its reuse. By this technique the data, which can specify up to 
four periods of time during the month of validity, is stored in the 
processor circuit 46 for comparison with the instantenous clock data 
output to enable television viewing during the four periods. 
Pay per view operation can be used in connection with pay per month 
operation. Where the two modes are to be used together, the pay per month 
data cards will have encoded on them four sub-periods of time during which 
viewing is not to be enabled as part of the normal monthly subscription 
service. Only if a pay per view data card is later inserted into the 
reader 1, which specifies one or more of the sub-periods as being 
permissible viewing time, can access to television programs be had during 
the sub-periods reserved on the monthly data card. By this method monthly 
service can be provided by subscription via a monthly data card which 
permits viewing on a single channel for the entire month except for 
certain predesignated sub-periods. Viewing during the predesignated 
sub-periods, which can be used to exhibit special broadcasts for which an 
extra charge is to be made, is then enabled by a separate data card, 
separately paid for, and intended to be read by the data card reader 1 
only once during the month after which the data on the pay per view card 
is erased. 
As the internal clock 47 within the processor circuit 46 provides output 
data indicative of current day and time, this information is compared by 
the comparator 53 with the data read from the monthly viewing card and 
additional data read from the pay per view card to determine whether or 
not an enable signal is to be provided on a specified channel at the 
current time. 
Multiple pay per view cards can be used with each pay per view card 
specifying one or more of the reserved sub-periods in the monthly period 
for viewing. Hence, if there are four special programs which are to be 
broadcast at predesignated times during the month, a subscriber can 
purchase a single data card 12 which will enable viewing of all four of 
the programs or he can purchase a datacard which will enable viewing of 
fewer than all four, e.g. one of the programs, and then later purchase one 
more additional cards to enable viewing of the remaining special programs. 
The cumulative sum of all of the time periods encoded on the multiple pay 
per view cards should not exceed the total number of time periods reserved 
during the monthly period of validity. 
A third mode of operation for which the processor circuit 46 can be adapted 
is termed wild card operation. A data card 12 encoded for wild card 
operation is preferably encoded with data specifying the month of validity 
and a sub-period time duration. The initiation of the sub-period is not 
limited to any particular time during the month but takes place 
immediately upon insertion of the data card 12 into the reader 1 during 
the month validity. Hence, a data card may specify two hours of operation 
during the month of January. A subscriber desiring to view two hours of 
television broadcast during the month of January would insert the data 
card 12 into the reader at the time he wished to view a broadcast and the 
processor would then provide an enabling signal to the channel whose 
designation was encoded on the data card 12 for a continuous period of two 
hours after which the enabling signal would be terminated. 
In the preferred embodiment of the invention, three channels of television 
viewing are provided for, each of which can be separately controlled by 
separate enable signals and respective security circuits. The three 
security circuits can be the same, e.g., all can be of the interference 
carrier type, or any two or all three of them can be different, e.g., one 
can be interference carrier, another synch suppression and the third STV. 
It is to be appreciated that the foregoing description is of a preferred 
embodiment of the invention suitable for use in providing access to 
subscription television services for predetermined periods of time. 
However, the invention has application to the provision of access to 
virtually any electrically controlled service for a predetermined period 
of time. For example, the apparatus of the present invention could be used 
in connection with a security device which enables or prevents entry of a 
person to a facility such as a building or a transportation vehicle such 
as a train. Hence, access to a library could be regulated by a 
subscription basis by the mere furnishing of properly encoded data cards. 
Commuters on metropolitan subways or rail systems could purchase data 
cards on a monthly basis which permit access to the transportation system 
at preselected periods of time during the month. For example, data cards 
permitting access on week days during rush hour periods could be sold at 
one rate while data cards only permitting access on off-peak hours or 
during weekends could be sold for a lesser charge. 
Although the invention has been described in connection with a preferred 
embodiment wherein three enable signals can be independently provided for 
controlling three channels of operation each of which can function in one 
of three modes, it is to be understood that within the teachings of the 
invention apparatus can be constructed for enabling fewer or greater 
numbers of channels than the three of the preferred embodiment. Moreover, 
while the modes of operation have been described in connection with a 
basic monthly renewable time period, other time periods of longer or 
shorter duration than the monthly period can be employed within the 
teachings of the invention sub-periods more than four in number and of 
duration beyond the 1/2 hour--16--hour range can also be provided within 
the teachings of the invention. Hence, it is to be appreciated that 
variations and modifications can be made to the preferred embodiment 
without departing from the spirit and scope of the invention which is set 
forth in the following claims.