JP2006203779A - Receiving terminal of catv system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiving terminal which can be easily installed in all the subscribers' houses and can instantaneously judge a modulation system of a digital broadcast signal at each subscriber's house in a CATV system for distributing the digital broadcast signal in a modulation form different by every area. <P>SOLUTION: The receiving terminal (STB) 32 to be installed in the subscriber's house of the CATV system is provided with demodulation parts 16, 18 for demodulating the digital broadcast signal of each modulation system set for every area. Then, the digital broadcast signal selected by a channel selection part 12 is demodulated by inputting it in each of the demodulation parts 16, 18 by channel selection processing executed by a microcomputer 30, the modulation system of the digital broadcast signal selected by the channel selection part 12 is specified from its demodulation result, output from the demodulation part 16 or 18 corresponding to the specified modulation system is inputted in a TS processing part 22 via a selection part 20 and the specified modulation system is identifiably displayed on a display part 36. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a receiving terminal device used in a subscriber home of a CATV system, and more particularly to a receiving terminal device capable of restoring broadcast data of an arbitrary broadcast channel from multi-channel digital broadcast signals having different modulation methods.

  Conventionally, in a CATV system, a set-top box (hereinafter referred to as STB) as a receiving terminal device is installed at a subscriber's home. This STB selects a TV broadcast signal of a specific broadcast channel from among multi-channel TV broadcast signals distributed from the center device of the CATV system to a subscriber's home via a transmission line composed of an optical cable, a coaxial cable or the like. The user can view a desired television broadcast program by designating the channel of the television broadcast signal to be selected and demodulated by the STB from the outside.

  By the way, in recent years, with the digitization of television broadcast signals distributed from broadcasting stations, digitization has also progressed in CATV systems. For example, on the center device side of CATV systems, television broadcast signals (digital broadcasting) distributed from broadcasting stations are advanced. Signal) is demodulated once for each channel, and the demodulated digital data is re-modulated with a modulation method specific to the CATV system (generally 64QAM) and then converted into a digital broadcast signal of a predetermined channel (that is, a predetermined transmission frequency band). Thus, a so-called trans-modulation CATV system for transmission to the terminal side has been put into practical use.

  In addition, for example, in the TV broadcast signal service form in the CATV system, a so-called reception failure countermeasure distribution service that distributes a TV broadcast signal to a reception failure area where radio waves from a broadcasting station are difficult to reach, satellite broadcasting and independent broadcasting In the CATV system that delivers multi-channel TV broadcast signals including the same, in a CATV system that performs these services at the same time, due to the charging control in the area where the urban service is performed, the reception failure area and other areas Thus, the modulation system of the television broadcast signal to be distributed is also changed.

  Specifically, in a reception failure area, a so-called pass-through method is adopted in which a digital broadcast signal distributed from a broadcasting station is directly transmitted to the terminal side so that a commercially available digital broadcast receiver can receive a terrestrial digital broadcast. However, in areas other than the reception failure area, the above-described trans-modulation method is used to retransmit the digital broadcast signal obtained by terrestrial digital broadcasting using a modulation method different between the reception failure area and the other areas. I am doing so.

  Further, in a large-scale CATV system, a reception facility provided at one place cannot cover a service area, and reception facilities may be distributed and arranged at a plurality of locations. In this case, the modulation system of the television broadcast signal (digital broadcast signal) transmitted from each receiving facility is not necessarily constant, and the modulation system of the transmitted digital broadcast signal may be different for each region as described above. .

Also, conventionally, in order to reduce the capital investment of digital receiving facilities in each CATV system, a plurality of distribution centers are connected by a network, and a television broadcast signal is distributed from each distribution center to the center device of each CATV system. Has also been proposed (see, for example, Patent Document 1). In this type of system, digital broadcast signals modulated by different modulation schemes are distributed from a plurality of distribution centers to each CATV system in order to meet various needs of each CATV system. A digital broadcast signal modulated by a different modulation method is transmitted to the transmission path of each CATV system.
JP 2004-186822 A

  By the way, as described above, in the CATV system in which the same digital broadcast signal is distributed by a different modulation method for each region, the STB installed in each subscriber's house is changed to the modulation method of the digital broadcast signal distributed in the region. Therefore, there is a problem that the installation work of the STB at the subscriber's house is troublesome.

  For example, a digital broadcast signal obtained by terrestrial digital broadcasting is distributed by either a pass-through method or a transmodulation method, and other digital broadcast signals obtained by satellite broadcasting or the like are distributed by a general transmodulation method. In the CATV system configured to do so, in addition to the digital broadcast signal distributed by the trans-modulation method, it is distributed to the subscriber premises in the region where the terrestrial digital broadcast signal is distributed by the pass-through method. STBs equipped with two types of demodulation circuits are installed so that digital broadcast signals can be demodulated, and STBs that can only demodulate digital broadcast signals distributed by the transmodulation method to subscriber premises in other regions STB to be installed at the subscriber's home for each region Must change the type, there is a problem that the installation work of the STB to the subscriber's home is troublesome.

  On the other hand, in order to prevent such a problem, the CATV system subscribers' homes are equipped with a plurality of demodulation circuits so that they can demodulate all the modulation system digital broadcast signals distributed by the system. The STB is installed, and the demodulator circuit used for demodulating the digital broadcast signal in the STB is set manually by the STB installation operator for each broadcast channel, or each STB itself is demodulated. A demodulation circuit used for demodulating a digital broadcast signal may be automatically set for each broadcast channel based on a demodulation result by the circuit.

  However, in this way, at each subscriber home, the type of the digital broadcast signal distributed to the subscriber home cannot be determined from the STB type or the like. When the signal reception situation deteriorates, there arises a problem that it takes time to identify the modulation system of the digital broadcast signal received at the subscriber's house and check the transmission system of the digital broadcast signal. .

  The present invention has been made in view of such problems, and in a CATV system in which a digital broadcast signal is distributed by a different modulation method for each region, it can be easily installed in all subscriber homes without troublesome setting work, Moreover, it is an object of the present invention to provide a receiving terminal device (STB) that can instantaneously determine the modulation method of a digital broadcast signal received at each subscriber's home.

  In the receiving terminal device according to claim 1, which has been made to achieve such an object, the channel selecting means is selected from among multi-channel digital broadcast signals transmitted from the center device of the CATV system via a transmission path. Selecting a digital broadcast signal of a specific broadcast channel designated by an external operation, and demodulating means demodulates the selected digital broadcast signal into the original digital broadcast signal before being modulated by the center device, The signal processing means processes the demodulated digital broadcast signal to restore broadcast data.

  In addition, the receiving terminal apparatus of the present invention is provided with a plurality of demodulation means corresponding to each modulation system as a demodulation means in order to demodulate each of a plurality of types of digital broadcast signals modulated by different modulation systems. The specifying means specifies the demodulating means that can normally demodulate the digital broadcast signal for each broadcast channel of the digital broadcast signal selected by the channel selecting means, and the selecting means specifies the demodulating means specified by the specifying means. Are selected as demodulation means used for demodulating the digital broadcast signal, and the output from the selected demodulation means is input to the signal processing means.

  Therefore, according to the receiving terminal device of the present invention, in the CATV system, even if the digital broadcast signal is modulated and distributed by a different modulation method for each area, all the subscribers' homes are of the same type. It is only necessary to install the receiving terminal device, and since it is not necessary to change the receiving terminal device installed in the subscriber's house for each area, the installation work can be easily performed.

  Further, in the receiving terminal device of the present invention, for each broadcast channel, a demodulation means that can normally demodulate a digital broadcast signal is automatically specified, and the signal processing means is demodulated by the specified demodulation means. Therefore, when the receiving terminal device is installed in the subscriber's house, the operator can use demodulation means for demodulating the digital broadcast signal for each broadcast channel. There is no need for manual setting, and this also simplifies the installation work at the subscriber's home.

  Next, in the receiving terminal device of the present invention, when the selecting means selects the demodulating means used for demodulating the digital broadcast signal, the selecting means selects the channel selecting means based on the type of the demodulating means selected. It is determined which of the plurality of modulation systems is the digital broadcast signal in, and the modulation system is displayed in an identifiable manner.

  For this reason, at the subscriber's home where this receiving terminal device is installed, it becomes possible to grasp the modulation method of the digital broadcast signal distributed to the subscriber's home from the display contents on the display means. When the reception status of the digital broadcast signal deteriorates at home, the operator operating the CATV system can hear from the subscriber the modulation method of the digital broadcast signal of the broadcast channel whose reception status has deteriorated, It becomes possible to quickly check the transmission system of the digital broadcast signal and identify the location where an abnormality has occurred, and to quickly perform recovery work when the abnormality occurs.

  Here, each time the channel selection unit selects a digital broadcast signal of a specific broadcast channel, the specifying unit may specify a demodulation unit that can normally demodulate the digital broadcast signal. Then, when the reception situation deteriorates and the digital broadcasting cannot be normally demodulated by all the demodulating means, the demodulating means that can normally demodulate the digital broadcasting signal (in other words, the digital signal selected by the tuning means) Broadcast signal modulation method) cannot be specified, and the digital broadcast signal modulation method cannot be displayed on the display means.

  Therefore, when the specifying means is configured in this way, when the reception situation deteriorates at the subscriber's home, the CATV system operator side displays the modulation displayed on the display means before the reception situation deteriorates from the subscriber. It is necessary to find out the method, but if the subscriber cannot remember the display contents, the subscriber cannot hear the modulation method of the digital broadcast signal of the broadcast channel whose reception status has deteriorated.

  For this reason, as described in claim 2, the specifying means specifies a demodulating means capable of demodulating a digital broadcast signal for each broadcast channel, and associates information representing the specified demodulating means with the broadcast channel. The storage means is configured to store the digital broadcast signal of the broadcast channel based on the information stored in the storage means by the specifying means every time the broadcast channel selected by the channel selection means is switched. What is necessary is just to comprise so that the demodulation means used for demodulating may be selected.

  In other words, if the specifying means and the selecting means are configured in this way, the display means will display the digital broadcast signal of the specific broadcast channel selected by the channel selecting means regardless of whether or not the demodulating means can successfully demodulate the digital broadcast signal (in other words, If this is the case, the digital broadcast signal modulation method can be displayed regardless of whether the reception status of the digital broadcast signal has deteriorated or not. When the reception situation deteriorates, it is possible to reliably hear from the subscriber the modulation system of the digital broadcast signal of the broadcast channel whose reception situation has deteriorated, and to quickly perform the restoration work.

  The demodulating means provided in the receiving terminal apparatus according to the present invention is, for example, a second demodulator for demodulating a digital broadcast signal modulated by the center apparatus using a modulation method peculiar to the CATV system. 1 demodulating means, and second demodulating means for demodulating a digital broadcast signal modulated at the broadcasting station side and transmitted without any change in the center apparatus.

Embodiments of the present invention will be described below.
FIG. 1 is a configuration diagram showing a configuration of a set top box (STB) 10 according to an embodiment to which the present invention is applied.

  Note that the STB 10 of the present embodiment receives the terrestrial digital broadcast distributed from the ground station and the digital satellite broadcast distributed via the broadcasting satellite (BS) or the communication satellite (CS) for each channel in the center device.・ Demodulate, remodulate the demodulated digital broadcast signals using a modulation method specific to the CATV system (64QAM in this embodiment), assign to a broadcast channel of a predetermined frequency band, and retransmit, and receive interference In a specific area where countermeasures should be taken, a digital broadcast signal obtained by terrestrial digital broadcast is retransmitted in the modulation scheme (specifically OFDM) received from the ground station without being remodulated by 64QAM. In the CATV system configured as described above, the receiving terminal device is used for installation in each subscriber's house.

  As shown in FIG. 1, the STB 10 of the present embodiment has an input terminal Tin for inputting a transmission signal transmitted from the center apparatus side of the CATV system via a coaxial cable, and is input to the input terminal Tin. A tuning unit 12 that selects a digital broadcasting signal of a specific broadcasting channel (hereinafter also simply referred to as a tuning channel) from the transmission signals and converts the frequency into an intermediate frequency band.

  The digital broadcast signal selected by the channel selection unit 12 and frequency-converted to the intermediate frequency band is divided into two by the distributor 14 and input to the OFDM demodulation unit 16 and the 64QAM demodulation unit 18, respectively.

  As a result, when the STB 10 is installed in a subscriber's house in a specific area where reception failure countermeasures are taken, the channel selection unit 12 selects a broadcast signal of terrestrial digital broadcasting transmitted from the center device by the pass-through method. The digital broadcast signal is demodulated by the OFDM demodulator 16. Further, even when the STB 12 is installed in a specific area where the reception failure countermeasure is taken, or even when the STB 12 is installed in the specific area where the reception trouble countermeasure is taken, the channel selection unit 12 is transmitted from the center apparatus by the transmodulation method. When a digital broadcast signal (that is, a broadcast signal other than terrestrial digital broadcast) is selected, the digital broadcast signal is demodulated by the 64QAM demodulator 18.

  Also, the STB 10 includes a demodulator 16 or 18 that can demodulate the original digital broadcast signal (specifically, transport stream: TS) before modulation on the center device side among the two demodulator 16 or 18. A selection unit 20 is provided for selecting the output (TS) from the input to the TS processing unit 22.

  The digital broadcast signal (TS) selected by the selection unit 20 is separated into video / audio / data etc. by the TS processing unit 22, and then input to the MPEG processing unit 24. The MPEG processing unit 24 Is converted into video and audio data.

  Also, the video and audio data obtained by the MPEG processing unit 24 are output to the video processing unit 26 and the audio processing unit 28, respectively, and are converted into video signals and audio signals by these units 26 and 28, respectively. The signal is output from the output terminal Tvo and the audio output terminal Tao to an external television receiver or the like.

  Furthermore, the STB 10 has an operation unit 32 for manually inputting various commands including a channel selection channel in the channel selection unit 12 and a remote control reception unit 34 for receiving a transmission signal from a remote control device (not shown) for remote operation. Is provided.

  The input signals from the operation unit 32 and the remote control reception unit 34 are input to a microcomputer 30 composed of a CPU, ROM, RAM, etc., and the microcomputer 30 selects from the operation unit 32 or the remote control reception unit 34. When a signal specifying a channel selection by the local unit 12 is input, the channel selection channel selected by the channel selection unit 12 is switched according to the specified signal, and then the digital broadcast signal selected by the channel selection unit 12 is selected. A channel selection process is executed in which the demodulator 16 or 18 capable of demodulating the TS is selectively operated and the selector 20 selects the output from the demodulator 16 or 18 that has been operated.

  In STB 10, the modulation system of the digital broadcast signal being selected by the channel selection unit 12 is a modulation system unique to the CATV system (that is, 64QAM) or a modulation system in terrestrial digital broadcasting (that is, OFDM). Or the like. The modulation unit for storing the display channel 36 in an identifiable manner by turning on the LED, the channel selection channel by the channel selection unit 12 and the modulation method of the digital broadcast signal in the channel selection channel. And a storage unit 38.

  When the microcomputer 30 first selects the digital broadcast signal of each broadcast channel after the STB 10 is installed in the subscriber's house by the channel selection process, the demodulator 16 , 18 recognizes the modulation system of the digital broadcast signal of the broadcast channel and writes it to the modulation system storage unit 38. Conversely, the modulation system storage unit 38 has a modulation system for the channel selection unit 12. When a digital broadcast signal of a broadcast channel that has already been written is selected, the modulation method of the digital broadcast signal is read from the modulation method storage unit 38, and the demodulation units 16 and 18 and the selection unit 20 are controlled and displayed. The modulation method is displayed on the unit 36.

Hereinafter, the channel selection process executed in the microcomputer 30 will be described with reference to the flowchart shown in FIG.
This channel selection process is a process that is repeatedly executed in the microcomputer 30 after the power to the STB 10 is turned on. When the process is started, the operation unit 32 or the remote control is performed in S110 (S represents a step). By determining whether or not a broadcast channel of a digital broadcast signal to be selected / demodulated by the STB 10 is input from the receiving unit 34 (that is, a selected channel (shown as a selected channel in the figure)), the selection is performed. Wait for the station channel to be input.

  When it is determined in S110 that a channel selection channel has been input, the process proceeds to S120, where a channel selection command for selecting a digital broadcast signal of the channel selection channel is output to the channel selection unit 12. As a result, the channel selection unit 12 selects a digital broadcast signal of a channel selected by the user via the operation unit 32 or a remote controller (not shown).

  Next, in S130, it is determined whether or not the channel of the channel selection command output to the channel selection unit 12 in S120 is a terrestrial digital broadcast channel. If the selected channel is not a terrestrial digital broadcast channel, the process proceeds to S140 to operate the 64QAM demodulator 18 and stop the operation of the OFDM demodulator 16, and in S150, the 64QAM demodulator After outputting the selection command for selecting the output from 18 to the selection part 20, the selection process is once complete | finished.

  That is, if the channel selection unit 12 is not a terrestrial digital broadcast channel, the channel selection unit 12 selects a digital broadcast signal modulated by 64QAM, which is a modulation method unique to CATV. In the series of processing of S150, the 64QAM demodulation unit 18 is operated so that the digital broadcast signal selected by the channel selection unit 12 can be reliably demodulated, and the selection unit 20 sends the 64QAM to the TS processing unit 22. The digital broadcast signal (that is, TS) demodulated by the demodulator 18 is selectively input.

  Next, when it is determined in S130 that the selected channel is a terrestrial digital broadcast channel, the process proceeds to S160, and the modulation system storage unit 38 stores the digital broadcast signal of the selected channel. It is determined whether or not a demodulation unit capable of demodulating the digital broadcast signal selected by the channel selection unit 12 has already been specified depending on whether or not the modulation method is stored.

  If it is determined in S160 that a demodulator capable of demodulating the digital broadcast signal selected by the channel selector 12 has not yet been specified, the process proceeds to S170, and the OFDM demodulator 16 and the 64QAM demodulator 18 are moved. The demodulating unit (OFDM demodulating unit 16 or 64QAM demodulating unit 18) that can demodulate the digital broadcast signal selected by the channel selecting unit 12 from the operating states of the demodulating units 16 and 18 in S180. And the modulation method of the digital broadcast signal corresponding to the specified demodulator 16 or 18 is stored in the modulation method storage unit 38 together with the current channel selection channel.

  Further, in this way, the modulation scheme of the current channel selection channel is stored in the modulation scheme storage unit 38 in S190, or the demodulation unit capable of demodulating the digital broadcast signal of the current channel selection channel is already in S160. If it is determined that the channel has been identified, the process proceeds to S190, and based on the modulation scheme of the current channel selection channel stored in the modulation scheme storage unit 38, the two demodulation units 16 and 18 are selected. The demodulation unit 16 or 18 capable of demodulating the digital broadcast signal selected by the local unit 12 is selected, the demodulation unit 16 or 18 is operated, and the operation of the other demodulation unit 18 or 16 is stopped.

  In S200, the selection unit 20 outputs a selection command for selecting the output from the demodulation unit 16 or 18 operated in S190 to the selection unit 20. The demodulated data (that is, TS) of the broadcast signal is selected, and in subsequent S210, the modulation method of the digital broadcast signal in the broadcast channel selected by the channel selection unit 12 is displayed on the display unit 36, and the channel selection process is performed. Is temporarily terminated.

  As described above, the STB 10 of the present embodiment includes a demodulating unit that can demodulate two types of digital broadcast signals with different modulation schemes transmitted from the center device side of the CATV system via a coaxial cable or the like. As shown, two types of demodulating units, an OFDM demodulating unit 16 and a 64QAM demodulating unit 18, are provided, and the channel selecting unit 12 selects a channel from the two demodulating units 16 and 18 by channel selection processing executed by the microcomputer 30. A demodulator capable of demodulating the digital broadcast signal is automatically selected.

  For this reason, in the CATV system of this embodiment, even if the transmission method of the digital broadcast signal of each broadcast channel in the terrestrial digital broadcast is set to one of the pass-through method and the transmodulation method for each region, It is only necessary to install the same type of STB 10 shown in FIG. 1 in each subscriber's house, and it is not necessary to change the STB installed in the subscriber's house for each region. Can do.

  The STB 10 of the present embodiment stores the transmission method of each broadcast channel in the terrestrial digital broadcast in the modulation method storage unit 38, and when the channel selection unit 12 selects the broadcast channel of the terrestrial digital broadcast, The digital broadcast signal modulation method of the broadcast channel is read from the modulation method storage unit 38, and the demodulation unit 16 or 18 capable of demodulating the digital broadcast signal is specified. At that time, the digital broadcast signal is read from the modulation method storage unit 38. Further, the modulation method of the terrestrial digital broadcast signal is displayed on the display unit 36.

  Therefore, in the subscriber house where the STB 10 is installed, the terrestrial wave distributed to the subscriber house from the display contents on the display unit 36 (specifically, the lighting state of the LEDs constituting the display unit 36). It becomes possible to grasp the modulation system of digital broadcasting for each broadcasting channel, and when the reception status of the broadcasting signal deteriorates at the subscriber's home, the operator operating the CATV system By listening to the modulation method of the terrestrial digital broadcast signal whose reception status has deteriorated from the subscriber, it is possible to quickly check the transmission system of the digital broadcast signal and identify the location where the abnormality has occurred. It becomes possible to work quickly.

  In the present embodiment, the OFDM demodulator 16 and the 64QAM demodulator 18 correspond to the demodulator of the present invention. In particular, the OFDM demodulator 16 corresponds to the second demodulator according to claim 3, The 64QAM demodulator 18 corresponds to the first demodulator according to claim 3. In the present embodiment, the TS processing unit 22, the MPEG processing unit 24, the video processing unit 26, and the audio processing unit 28 correspond to the signal processing means of the present invention.

  On the other hand, in the channel selection process executed by the microcomputer 30, the process of S120 for outputting a channel selection command to the channel selection unit 12 realizes the function as the channel selection means of the present invention together with the channel selection unit 12. The processing of S170 and S180 corresponds to the specifying unit of the present invention, and the modulation method storage unit 38 corresponds to the storage unit of the present invention. Further, the processing of S190 and S200 in the channel selection processing realizes the function as the selection means of the present invention together with the selection unit 20, and the processing of S210 realizes the function as the display means of the present invention together with the display unit 36. is doing.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect can be taken in the range which does not deviate from the summary of this invention.
For example, in the above-described embodiment, the STB 10 used in the CATV system in which each terrestrial digital broadcast signal is transmitted in a different modulation method for each region has been described. However, the receiving terminal device of the present invention receives a satellite broadcast. Even in the CATV system configured to transmit the digital broadcast signal obtained by doing so and the digital broadcast signal for independent broadcasting by a different modulation method for each region, it is applied similarly to the STB 10 of the above embodiment. be able to.

It is a block diagram showing the structure of the set top box (STB) of embodiment. 3 is a flowchart showing a channel selection process executed in the STB of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... STB, Tin ... Input terminal, 12 ... Channel selection part, 14 ... Distributor, 16 ... OFDM demodulation part, 18 ... 64QAM demodulation part, 20 ... Selection part, 22 ... TS processing part, 24 ... MPEG processing part, 26 ... Video processing unit, Tvo: video output terminal, 28: audio processing unit, Tao: audio output terminal, 30: microcomputer, 32: operation unit, 34: remote control receiving unit, 36: display unit, 38: modulation method storage unit.

Claims (3)

A channel selection means for selecting a digital broadcast signal of a specific broadcast channel designated by an external operation from among multi-channel digital broadcast signals transmitted from a center device of a CATV system via a transmission path;
Demodulating means for demodulating the digital broadcast signal selected by the channel selecting means into the original digital broadcast signal before being modulated by the center device;
Signal processing means for processing the digital broadcast signal demodulated by the demodulation means to restore broadcast data;
A receiving terminal device of a CATV system comprising:
In order to demodulate each of a plurality of types of digital broadcast signals modulated by different modulation schemes, the demodulation means includes a plurality of demodulation means corresponding to each modulation scheme,
Identifying means for identifying the demodulating means that can normally demodulate the digital broadcast signal among the plurality of demodulating means for each broadcast channel of the digital broadcast signal selected by the channel selecting means;
A selecting means for selecting the demodulating means specified by the specifying means as a demodulating means used for demodulating the digital broadcast signal, and inputting an output from the selected demodulating means to the signal processing means;
Based on the type of demodulation means selected by the selection means, the channel selection means determines which of the plurality of modulation systems the digital broadcast signal being selected is, and displays the modulation system in an identifiable manner Display means to
A receiving terminal apparatus for a CATV system, comprising: The specifying means specifies a demodulating means capable of demodulating the digital broadcast signal for each broadcast channel, stores information representing the specified demodulating means in association with the broadcast channel in a storage means,
The selection means selects a demodulation means used for demodulating a digital broadcast signal of the broadcast channel based on the information stored in the storage means every time the broadcast channel selected by the channel selection means is switched. The receiving terminal apparatus of the CATV system according to claim 1. As the demodulation means,
A first demodulating means for demodulating a digital broadcast signal modulated by the center apparatus in a modulation method specific to the CATV system;
Second demodulating means for demodulating a digital broadcast signal that is modulated on the broadcast station side and transmitted without any change in the center device;
The receiving terminal apparatus of the CATV system according to claim 1 or 2, characterized by comprising:

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