| 摘要 |
<p>A system for automatically monitoring the programs broadcast by network affiliated broadcasting stations includes a plurality of remote monitoring sites, each associated with one of the broadcasting stations, and a central unit for periodically interrogating the remote monitoring units. Each remote monitoring unit contains apparatus for monitoring program identifying data transmitted during the vertical intervals of network generated programs, and for storing the data in a change format. In the change format, the data is stored only when a change occurs in predetermined bits of the program identifying data, or when a change between a coded and an uncoded program transmission occurs. An elapsed time clock is provided in each remote monitoring unit for generating a record of the elapsed time between program changes to permit the broadcast time of a program to be calculated. The broadcast time may then be compared with the time of origin of the program, which is included in the program identifying data, to permit delayed broadcasts to be identified. Each remote monitoring unit is controlled by a mini-computer having a read-only memory and a random-access memory. The data in the read-only memory serves to establish communications with the central unit in order to permit the central unit to access the random-access memory. After the random-access memory has been accessed, the central unit may read the program identifying data stored in the randomaccess memory, or may remotely reprogram the random-access memory. In a typical system, the remote monitoring unit is interrogated once per day, and the data is transmitted to the central unit in blocks having a length selected to minimize the probability of an error occurring in each block. Error checking bits are included in each block to permit the central unit to check end block for accuracy and to request a retransmission in the event that an error is found. Similar error checking programs are included in the remote monitoring unit to minimize the possibility of an error occurring when the remote monitoring unit is being reprogrammed by the central unit.</p> |
