Abstract:
A device which monitors information contained in broadcast electrical signals and which, when attached to or combined with the circuitry of a television, radio or other receiver, will automatically prevent reception of unwanted material.

Description:
BACKGROUND OF THE INVENTION 
     This invention pertains to broadcasting and relates more particularly to a device for automatic elimination of unwanted program material from the content of radio, television or other broadcast signals. 
     OBJECTS 
     Among the objects of my invention is to provide a device which will eliminate unwanted material, such as commercial announcements, from the content of radio, television or other signal transmission. 
     A further object of the present invention is for such device to be compatible with existing receivers so that the use of said device, together with existing receivers, will not require circuitry modification to the existing apparatus. 
     Other objects and advantages reside in the details of construction and operation as are more fully hereafter described and claimed, reference being had to the accompanying drawings forming a part thereof wherein like numerals refer to like parts throughout and in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a generalized block diagram of the invention. 
     FIG. 2 shows a more specific application of the device in conjunction with television signals. 
     FIG. 3 shows a more specific application of the device in conjunction with radio signals. 
     FIG. 4 plots signal amplitude vs. time and shows a form of phased operation of the invention. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     As shown in FIG. 1, the system for this invention includes: an analog to digital converter (2) for sampling the input signal and converting its content to digital form; an input signal; a synchronization clock (3) for controlling the operation of the analog to decimal converter relative to time; storages (5) and (6) for storing portions of the output of the analog to decimal converter (2); a programming switch (4) for selecting the specific portions of the output of analog to digital converter (2) for storage; a comparison unit (7) for comparing subsequent output of analog to digital converter (2) with the content of storages (5) and (6); a signal output; an alternate signal (9); and a source selection switch (8), for switching the signal output (output signal) between the input signal and alternate signal (9); which are interconnected as follows: Input signals are sent to the input of analog to digital converter (2) and to input n of the source selection switch (8). The output of synchronization clock (3) is connected to the analog to digital converter (2) as to control its operation in sampling and converting the analog input signals received by the analog to digital converter (2) into a output which contains discreet digital words and is connected to the input of comparison unit (7) and, via commit to memory switch (4), to storage (5). Interconnection between comparison unit (7), commit to memory switch (4), storage (5), the output of comparison unit (7) and the control element of source selection switch (8) is made so that the comparison unit (7), when finding a match between a digital word sent to it by analog to digital converter (2) and one of the words previously stored in memory (5), causes source selection switch (8) to switch its output from input n, the input signal, to input p, to which has been connected alternate signal (9). It can be readily appreciated that the use of two storage units will significantly reduce the word storage capacity required of the system, particularly when the unwanted signal elements are characterized as each being several words long. In such case, and with the use of two storage units, shown as elements (5) and (6) in FIGS. 1, 2 and 3, only the beginning and end word need be stored, a match with a word in storage (5) or (6) would signal the start or end, respectively, of the unwanted transmission. In this preferred embodiment comparison unit (7) causes source selection switch to (8) to continuously output the alternate signal (9) from the time a word digitalized from the input signal matches one of the words previously committed to storage (5), corresponding to the start of unwanted input signal content, until a subsequent, end of unwanted transmission, match is found with storage (6); without the requirement of additional, interim, matches. If desired, the device can be operated with only one storage; however, the inclusion of the above-mentioned second storage is preferred and is highly desirable for the most efficient utilization of the system. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In operation the device utilizes the fact that, as shown in FIG. 1, all signals containing program information vary relative to time, as shown in the plot (1) of signal vs. time. 
     In the invention the input signal is fed into an analog to digital conversion unit (2) which, working together with a synchronization clock (3) converts the analog form of the input signal content to digital form, assigning a numerical value to the amplitude of the signal at one or more reference points in time, such points being generated by a synchronization clock (3) and shown as reference points a, b, c, d, e and f in plot 1. 
     Although in practice any number or sequence of reference points can be chosen, the given example shows five points in the start-to-end period of sample, wherein reference point a has a numerical value of 8; b, a value of 1, c-3; d-0 and e-6. As more fully described below, the synchronization clock is set to begin each sample period at a predetermined interval, complete the sequence, and then start the next sample period. 
     By assigning each reference point a position as a digit in a number having the same number of digits as reference points, the value of the five-digit number generated by the sampled portion of input signal in the example is thus 81,306. If the sampled signal had been a part of unwanted program material, i.e. the beginning of an unwanted commercial message, the user would, by means of a commit to memory switch (4) program the operation of source selection switch 8 to begin elimination from the signal output of the unwanted program material by directing direct the associated numerical generation (81,306 in the example) to storage unit (5). The user would also program the operation of the source selection switch 8 to reconnect the input signal to the signal output by directing the numerical generation associated with the end of the unwanted signal to storage unit (6). Then upon setting switch (4) to comparison, or normal, operation, the five-digit numbers subsequently generated, will be constantly compared, by means of comparison unit (7) to the numbers in storage. Thus programmed, upon repeat reception of a signal previously found to be undesirable, the five-digit number so generated would equal one of the numbers previously committed to storage (5) causing the comparison unit (7) to trigger the operation of a source selection switch (8) to blank out or eliminate the unwanted signal, or optionally select an alternate signal (9). Subsequent numerical sequences generated by the incoming signal would then be compared to storage (6) where the next matched number would reset the receiver&#39;s output to the original program source. 
     In the inventor&#39;s preferred embodiment, a first digit comparator (13), as shown in FIGS. 2 and 3, has been interconnected to the analog to digital conversion unit (2), the comparison unit (7) and the synchronization clock (3). The purpose of this comparator is to provide a self-adjusting datum level against which incoming signals can be compared, thus preventing erroneous readings due to variations in transmission or receiver adjustment. In operation, the first digit of each sequence is not sent to the comparison unit (7). Rather, it is held for comparison against each succeeding digit of the sequence and the difference between them, or delta, sent to comparison module (7). Pulses are also generated by the synchronization clock (3) coincident with the end of each sequence. These pulses are used to clear the storage of the first digit comparator (13), and make it available for storage of the first digit of the following sequence. 
     In the case of television reception, as shown in FIG. 2, the clock (3) is kept in synchronization by means of deflection pulses received with the video picture. In the embodiment shown, vertical deflection pulses (10) used to bring the picture tube electron beam back to the top of the screen are inputed to the clock (3) and synchronize it with respect to the beginning of each sample period. FIG. 2 also shows the optional use of a sender (15) and a receiver (16) used, via path a-a, to transmit instructions from comparison unit (7) to source selection switch (8), it being intended to illustrate that by means of such arrangement, the source selection switch (8) may be operated by a remotely placed comparison unit (7). Alternately, path b-b between comparison unit (7) and source selection switch (8) shows the conventional hard-wire means of interconnection. 
     In radio reception, as shown in FIG. 3, the clock (3) is kept in synchronization by means of pulses (12) generated and inputed to it by a no-signal-trigger (11). This trigger, interconnected to the input of analog to digital converter (2), monitors the received signal, and generates a pulse each time the level monitored is equal to a preset value, i.e. zero, as received due to the pauses between spoken words. Each pulse thus triggered is sent to, and causes the synchronization clock (3&#39;) to start a new sequence. To allow for the fact that the numerical generation subsequently produced may also contain zeros, such as that in the given example of 81,306, and that such zeros can represent either a valid digit of the number to be compared or the proper start of a new sequence, a multiphase clock (3&#39;) and a multiphase first digit comparator (13&#39;) are employed, the phase of the clock (3&#39;) and first digit comparator (13&#39;), as well as entry to a corresponding comparison unit, interconnected to, and controlled by, phase switch (14), in turn interconnected to and operated by pulses generated by the no-signal-trigger (11). 
     As shown in FIG. 4, the number 81,306 would be sent to comparison unit (7A), the number 61,056 to (7B) and so on. In addition, because in the given example, the number 81,306 has previously been programmed into storage (4) as the beginning of an unwanted message, comparison unit (7A), upon finding the match, will trigger the source selection switch (8) to blank the unwanted signal. The need for multiphase capability in both the clock (3&#39;) and the first digit comparator (13&#39;) is shown in FIG. 4 where it can be seen that sequence IV is out of phase with sequence III, thus requiring separate synchronization generation for each sequence. It is to be observed that the elements disclosed are substantially standard equipment which need not be specifically illustrated for those skilled in the art and, by themselves, form no part of the present invention outside of the system as disclosed. The specific operating characteristic of each element required is affected by the construction and design of the electrical components immediately preceeding and following the respective element. For example, comparison unit (7), as herein disclosed, when used with both storages (5) and (6), incorporates logic circuitry to enable it to search storage (5) alternately with storage (6); such logic may be built into one particular comparison unit while another would require an external logic source. Similarly, the designs of selection switch (8) and comparison unit (7) are interdependent; a latching relay used as source selection switch (8) will switch between inputs with a pulsed output from comparison unit (7), while other families of switch may require continuous control outputs from the comparison unit. 
     The foregoing description is intended to be illustrative only and not to be interpreted in the limiting sense.