Abstract: A scrambled broadcast system including a scrambler having a first generator for generating a first redundancy added data by adding a first redundancy data which changes over time to a message data, a second generator for generating a second redundancy added data by adding a second redundancy data which is obtained by executing a predetermined operation to the first redundancy added data generated in tho first generator, and an encryptor for executing a predetermined encrypting processing to the second redundancy added data generated in the second generator, a descrambler having a restoring unit for restoring the second redundancy added data by decrypting the encrypted data output from the decryptor, a discriminator for discriminating whether the operation operated in the second generator is realized to the second redundancy added data restored in the restoring unit or not and discriminating the rightness of the message data which is made by removing the first and the second redundancy data from the second red

Abstract: An error detecting/correcting circuit 9 in a digital broadcast receiving device calculates a error rate from the error amount for the amount of input information. A controlling part 15 converts the error rate into the C/N ratio as a receiving signal quality and indicates it on a screen of a TV receiver 5 or other indicator 18. In this method, after digitally demodulating the received digital broadcasting signal, the error rate is obtained by an error detecting part 9 and the error rate is converted into the receiving signal quality for indication. Therefore, compared with the reception performance indication based on the input level such as the AGC voltage, the method is high both in precision and in stability. The receiving signal quality can be detected only while receiving a digital broadcasting signal, so with reference to the converted receiving signal quality in antenna bearing adjustment, a digital broadcasting signal can be surely received without confusing it with an analog broadcasting signal.

Abstract: Television signal transmission and reception system includes a broadcasting center, a transmission network and many reception terminals. In the broadcasting center, plural television signals corresponding to individual channels are modulated into transmittable form, and a synthesis circuit synthesizes the television signals to produce a synthesis image signal for a multi-screen display comprising plural small screens. Both the ordinary television signal and the synthesis image signal is transmitted with control information to the reception terminals through the transmission network. In the reception terminal, for selecting a desired channel out of the individual channels, the synthesis image signal is used for displaying a multi-screen, a moveable cursor image is superimposed on the multi-screen for designating one small screen corresponding to the desired channel.

Abstract: In a cable television system having a two-way communication function in which downstream signals are transmitted from a broadcasting center to a plurality of terminals, upstream signals are transmitted from the plurality of terminals to the broadcasting center, and the broadcasting center and the plurality of terminals receive and demodulate the transmitted signals, a level detector of each terminal obtains a level detection signal by detecting the level of a downstream signal from the broadcasting center. A controller stores a level setting signal exhibiting a level change of negative linear characteristics with respect to the level of the downstream signal. The controller includes a level setting function for setting the transmission level of the upstream signal output from a communication signal modulator on the basis of the level setting signal.

Abstract: A train of pulses within a predetermined cycle is produced at a first port of a microcomputer when the microcomputer is operating normally. An operational amplifier compares a voltage obtained by rectifying the pulse train with a reference potential. The microcomputer is reset, depending on the comparison result obtained at the output terminal of the operational amplifier. The output of a power supply circuit is used as a reference potential. When an overcurrent flows in peripheral circuits connected to the microcomputer, the output voltage of the power supply circuit is decreased. This decrease varies the reference potential applied to the operational amplifier. The microcomputer outputs a power supply control pulse from a second port, after it is reset. A relay turns off the power of the power supply circuit to the peripheral circuits.

Abstract: Television signal transmission and reception system includes a broadcasting center, a transmission network and many reception terminals. In the broadcasting center, plural television signals corresponding to individual channels are modulated into transmittable form, and a synthesis circuit synthesizes the television signals to produce a synthesis image signal for a multi-screen display comprising plural small screens. Both the ordinary television signal and the synthesis image signal is transmitted with control information to the reception terminals through the transmission network. In the reception terminal, for selecting a desired channel out of the individual channels, the synthesis image signal is used for displaying a multi-screen, a moveable cursor image is superimposed on the multi-screen for designating one small screen corresponding to the desired channel.