JPH06225304A - Terminal device for CATV - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a CATV terminal device for detecting a signal level of a cable broadcasting, and it is not abnormal even if the carrier level is lowered at midnight or early morning, or the carrier level is maintained for a long time. The purpose of the present invention is to make it possible to make an accurate determination of an abnormality in the network, such as making an abnormality when there is a level drop, or making an abnormality when the carrier can be detected but lower than the normal level. A CATV terminal device 13 is provided with a signal level detecting unit 18 for receiving a cable broadcast and detecting a signal level of the carrier, and the carrier level received by the signal level detecting unit 18 of the CATV terminal device 13 is It is configured to detect an abnormality in the received signal level drop when the value is less than the normal value and is in the operating hours.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV terminal device for detecting a signal level of cable broadcasting.

[0002]

2. Description of the Related Art Conventionally, in a CATV system as shown in FIG. 7, the signal level of the subscriber at the final stage of the network must be kept above a reference value. Therefore, in the terminal device installed in the subscriber, the signal level is monitored, and if there is an abnormality, the fact is displayed and the center is notified. The configuration and operation of FIG. 7 will be briefly described below.

FIG. 7 shows an explanatory view of the prior art. In FIG. 7, a center 21 receives a TV broadcast wave, sends out a modulated signal and the like to the coaxial network 25, and is composed of a TV modulator 22, a scrambler 23, a high output amplifier 24, and the like. Is.

The TV modulator 22 frequency-modulates the received video signal for frequency multiplexing. The scrambler 23 scrambles the video signal in order to prevent wiretap viewing.

The high output amplifier 24 amplifies the modulated signal and sends it to the coaxial network 25. CA
The TV terminal 26 demodulates a signal received via the coaxial network 25, descrambles it, and displays an image on the TV 27.

The TV 27 displays an image.
Next, the operation will be described. (1) The signal sent from the center 21 to the coaxial network 25 is gradually attenuated and the subscriber's CATV terminal 26
Enter, demodulate and display an image on the TV 27.

(2) When the image of (1) is displayed on the TV 27, the signal level (pilot signal or channel carrier) of the subscriber is also monitored to see if it is above the reference value. Contact.

[0008]

As described above, the CA
In the TV system, since the signal level of the subscriber at the final stage of the network must be above the reference value, the TV system monitors whether the pilot signal in the signal or the carrier of the channel actually being viewed is above the reference value. When it is below the reference value, the fact is notified to the center 21. Therefore, when the program ends at midnight, there is a problem that the carrier is stopped and the abnormality is detected at this time as well.

The present invention solves these problems.
Even if there is a decrease in the carrier level at midnight or early morning, it is not abnormal, or if there is a decrease in the carrier level for a long time, it is abnormal, or if the carrier can be detected but it is lower than the normal level, it is abnormal. The purpose is to enable accurate determination of network abnormalities.

[0010]

FIG. 1 is a block diagram showing the principle of the present invention. In FIG. 1, a CATV terminal device 13
Is a terminal device for receiving cable broadcasting, and here,
Signal level detector 18 for detecting the signal level of the carrier
And so on.

The signal level detector 18 detects the signal level of the received carrier.

[0012]

According to the present invention, as shown in FIG. 1, when the level of the carrier received by the signal level detection unit 18 of the CATV terminal device 13 is equal to or lower than the normal value and during the operating time, the received signal I am trying to detect that the level is low.

Further, when the level of the carrier received by the signal level detection unit 18 of the CATV terminal device 13 is equal to or lower than the normal value and continues for a predetermined time or longer, it is detected that the level of the received signal is low. ing.

Further, when the level of the carrier received by the signal level detecting unit 18 of the CATV terminal device 13 is equal to or lower than the normal value and the carrier can be detected, the carrier cannot be detected and the carrier is in the operating time zone. When it cannot be detected and is not in the operating time zone and continues for a predetermined time or longer, it is detected that the level of the received signal is low.

Further, when it is detected that the level of the received signal is low, the alarm data having the set contents is automatically transmitted to the center for notification. Therefore, it is not abnormal even if the carrier level drops at midnight or early morning, or abnormal when the carrier level drops for a long time, or abnormal when the carrier can be detected but is lower than the normal level. By doing so, it becomes possible to accurately detect an abnormal drop in the signal level of the network and to automatically notify the center to that effect.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the construction and operation of an embodiment of the present invention will be described in detail with reference to FIGS.

FIG. 1 is a block diagram showing the principle of the present invention. Figure 1
1, the center 1 scrambles the received signal and sends the scrambled signal to the coaxial network 10. The TV modulator 2 frequency-modulates the received signal, and scrambles the video signal to prevent snooping. It comprises a scrambler 3 for multiplying, a mixer 4 for mixing a video signal and a control signal, and a high output amplifier 9 for amplifying.

The subscriber telephone line network is a CATV terminal device 1.
The alarm data and the like from 3 are transmitted to the center 1. The coaxial network 10 distributes the signal transmitted from the high output amplifier 9 to the CATV terminal device 13.

The CATV terminal device 13 is installed in the subscriber's house and watches the received signal on the TV 14. Here, the CATV terminal device 13 is composed of a signal level detection unit 18 for detecting the level of the received signal and the like. It is what is done.

FIG. 2 shows a block diagram of an embodiment of the present invention.
In FIG. 2, the center 1 scrambles a received signal or a signal (not shown) and sends the scrambled signal to the coaxial network 10.
It provides a video service of a plurality of channels, and includes a TV modulator 2, a scrambler 3, a mixer 4, and an FSK.
The modulator 8 and the high output amplifier 9 are included.

The TV modulator 2 frequency-modulates a signal received by radio waves or the like. Scrambler 3
Is for scrambling the video signal, descrambling it on the subscriber side to demodulate it to the original signal, and preventing wiretapping.

The mixer 4 receives the signal from the TV modulator 2 and
The signal from the FSK modulator 8 is mixed. The high output amplifier 9 amplifies the signal mixed by the mixer 4 and sends it to the coaxial network 10.

The subscriber telephone line network 5 is for transmitting alarm data from the CATV terminal device 13, here, to the communication control device 6 on the center side. The communication control device 6 communicates with the CATV terminal device 13 on the subscriber side via the subscriber telephone line network 5 or the like, and here receives as alarm data when the carrier level of the signal is low. Yes (see (c) alarm data in FIG. 6).

The control computer 7 is a computer for performing various controls on the center side. In this case, the communication control device 6 is used by the subscriber's CATV via the subscriber telephone line network 5.
When alarm data or the like is received from the terminal device 13 for use, its content is taken out and analyzed, and various controls are performed based on the result, or the signal is passed through the FSK modulator 8, the mixer 4 and the high output amplifier 9. Are transmitted.

The FSK modulator 8 is a frequency modulator, which frequency-modulates various data and sends it to the coaxial network 10 via the mixer 4 and the high-power amplifier 9.

The coaxial network 10 includes a high output amplifier 9
It is for distributing the signal transmitted from each subscriber to each subscriber. The tap-off 11 is for branching a signal from a line having the coaxial network 10 to a subscriber.

The protector 12 is a protector when the signal branched by the tap-off 11 is taken into the subscriber's house. The CATV terminal device 13 is provided in the subscriber's house and has a configuration as shown below. The distribution 15, the RF MOD / DEM 16, the TV tuner 17,
Signal level detector 18, descrambler 19, F CO
The V20, the clock unit 21, the CPU 22, the memory 24, the buttons 26, the remote control reception 27, and the like are included.

The distribution 15 takes in a signal from the coaxial of the coaxial network 10 and distributes it. Where tv
Distribute to tuner 17 and RF MOD / DEM 16. The RF MOD / DEM 16 is a modulator / demodulator,
The signal (high frequency signal) distributed by the distribution 15 is demodulated here to take out a data signal and pass it to the CPU 22.

The TV tuner 17 demodulates and extracts the signal of the designated channel from the signal (high frequency signal) distributed by the distribution 15. The signal level detector 18 detects the signal level of the carrier of the received signal demodulated by the TV tuner 17, and notifies the CPU 22 of the signal level.

The descrambler 19 is a TV tuner 17
The signal of the designated channel demodulated by is descrambled and returned to the original viewable signal. F
The COV 20 is a frequency converter, which frequency-modulates the signal descrambled by the descrambler 19 and sends it to the TV 14.

The clock section 21 measures the time. The CPU 22 performs various controls according to a program, and is composed of an abnormality detection process 23 and the like here.

The abnormality detection processing 23 is performed by the signal level detection unit 1
It is to detect whether the signal level of the carrier detected by 8 is abnormal (which will be described later with reference to FIGS. 3 to 5).

The memory 24 stores programs and data, and here stores the carrier level determination table 25 (see (b) of FIG. 6). The carrier level determination table 25 is a table (see (b) in FIG. 6) in which conditions for determining whether the carrier level is abnormal are set. Here, for example, as shown in FIG. 6, a normal value of the carrier level: eg 60 μV, a normal time when the carrier is transmitted: eg from 6 o'clock to 23:00, a time during which the carrier is continuously transmitted: eg 7 hours Noise level: For example, set to 20 dBμV.

The button 26 is a button for performing various operations. The remote control reception 27 is for receiving an instruction from the remote control 28 and performing various operations.

Next, the operation of the configuration of FIG. 2 will be described in the order shown in the flowchart of FIG. This is for transmitting alarm data to the center 1 or the like when the carrier level is below the normal value and during the operating hours.

In FIG. 3, S1 determines whether the carrier level is a normal value or higher. This is the CA of the subscriber's home in FIG.
It is determined whether the signal level of the currently received carrier detected by the signal level detection unit 18 of the TV terminal device 13 is equal to or higher than the normal value set in the carrier level determination table 25. If YES, the carrier level is found to be normal, so S1 is repeated. On the other hand, in the case of NO, the carrier level is not normal (abnormal) and it is determined that the carrier level is not higher than the normal value level, so the process proceeds to S2.

In step S2, it is determined whether the current time is 6:00 to 23:00. Since the carrier level of the signal currently being received is found to be equal to or lower than the normal value in S1 NO, it is determined whether the present time is the operating time zone, for example, 6 to 23:00 (this operating time zone will be described later. (6) (b) carrier level determination table 25 is set to time 6:00 and time 23:00). In the case of YES, ・ NO in S1 indicates that the carrier level is below the normal value. ・ YES in S2 reveals that the current time is the operating time zone (for example, from 6:00 to 23:00), so an alarm is sent to the center 1 in S3. That is, the alarm data shown in FIG. 6C is transmitted to the center 1 via the subscriber telephone line network 5. On the other hand, in the case of NO, the current time is not in the operating time zone, and therefore the process returns to S1.

As described above, when the carrier level of the signal received by the CATV terminal device 13 at the subscriber's house is below the normal value and the current time is in the operating time zone, the alarm data is transmitted to the center 1 or the like, Notifies that the signal level has dropped below the normal value.

Next, the operation of the configuration of FIG. 2 will be described in the order shown in the flowchart of FIG. This is to transmit alarm data to the center 1 or the like when the carrier level is equal to or lower than the normal value and has continued for a predetermined time (for example, 7 hours).

In FIG. 4, in S11, it is determined whether the carrier level is a normal value or higher. This is C at the subscriber's house in FIG.
The signal level of the currently received carrier detected by the signal level detection unit 18 of the ATV terminal device 13 is
It is determined whether the value is not less than the normal value set in the carrier level determination table 25. If YES, the carrier level is found to be normal, so S1 is repeated. On the other hand, in the case of NO, the carrier level is not normal (abnormal) and it is determined that the carrier level is not higher than the normal value level, so the process proceeds to S2.

In step S12, it is determined whether the operation is continued for 7 hours. This is because the carrier level of the signal currently being received is found to be equal to or lower than the normal value at NO in S11, and it is determined whether the carrier level is equal to or lower than the normal value for 7 hours at the present time (this 7-hour continuation will be described later). (Continuation time is set to 7:00 in the carrier level determination table 25 of FIG. 6B). Yes
In the case of: ・ NO in S11, the carrier level is below the normal value ・ YES in S12, the carrier level was found to be below the normal value for 7 hours continuously, so an alarm is sent to the center 1 in S13,
That is, the alarm data of (c) of FIG.
To the center 1 via. On the other hand, if NO,
Since it has not continued for 7 hours at the current time, the process returns to S11.

As described above, when the carrier level of the signal received by the CATV terminal device 13 at the subscriber's house is below the normal value and it continues for 7 hours, the alarm data is transmitted to the center 1 and the signal level is normal. Notify that the value has dropped below the value.

Next, the operation of the configuration of FIG. 2 will be described according to the order shown in the flowchart of FIG. When the carrier level is below the normal value and the carrier can be detected, the carrier level is below the normal value, the carrier cannot be detected, and the operating time zone (6
When the carrier level is below the normal value, the carrier cannot be detected, and it is not in the operation time zone (6:00 to 23:00), and continues for a predetermined time or longer (7 to 23:00).
The alarm data is transmitted to the center 1 or the like when any one of the above (when the time is continued) is met.

In FIG. 5, in S21, it is determined whether the carrier level is higher than the normal value. This is C at the subscriber's house in FIG.
The signal level of the currently received carrier detected by the signal level detection unit 18 of the ATV terminal device 13 is
It is determined whether the value is not less than the normal value set in the carrier level determination table 25. If YES, the carrier level is found to be normal, so S21 is repeated. On the other hand, in the case of NO, the carrier level is not normal (abnormal), and it is determined that the carrier level is not higher than the normal value level.

In step S22, it is determined whether the carrier level can be detected. In the case of YES, it is found that the carrier level is below the normal value and is within the detectable range.
At 25, the alarm data is transmitted to the center 1. On the other hand, N
In the case of O, the process proceeds to S23.

In step S23, it is determined whether the current time is from 6:00 to 23:00 (operating hours). If YES, the current time is 6 o'clock
Since it is determined to be 23:00 (operating hours), alarm data is transmitted to the center 1 in S25. On the other hand, in the case of NO, the processing proceeds to S24.

In step S24, it is determined whether the operation is continued for 7 hours (continued for a predetermined time or longer). In the case of YES, since it is determined that the operation is continued for 7 hours (the operation is continued for the predetermined time or more), the alarm data is transmitted to the center 1 in S25. On the other hand, if NO, S2
Return to 1.

As described above, when the signal received by the CATV terminal device 13 at the subscriber's house is: -The carrier level is below the normal value and the carrier level is detected-The carrier level is below the normal value, and The carrier level is not detected and the current time is in the operating hours (6:00 to 23:00)
When the carrier level is below the normal value, the carrier level is not detected, the current time is not in the operating time zone (6:00 to 23:00), and continues for a predetermined time or longer (7 hours continues) , The alarm data is transmitted to the center 1 to notify that the signal level has dropped below the normal value.

FIG. 6 shows an operation explanatory diagram of the present invention. Figure 6
(A) indicates the carrier level. Here, the horizontal axis represents the frequency f, and the vertical axis represents the reception intensity dBμV. The carrier is a signal for carrying a video signal. Here, the normal value of the carrier level received by the CATV terminal device 13 at the subscriber's house is set to 60 dBμV in the carrier level determination table 25 here.

FIG. 6B shows an example of the carrier level judgment table 25. This is a table preset in the terminal device 13 for CATV of FIG. 2, and as shown in the figure: -Normal value 60 dBμV-Time 6: 00-Time 23: 00-Continuation time 7: 00-Noise level 20 dBμV Set in advance. An arbitrary value can be set by changing the value set here.

FIG. 6C shows an example of alarm data. This is because the CATV terminal device 13 uses the subscriber telephone line network 5 and the communication control device 6 to control the computer 7.
It is an example of the format when notifying to. Here, STX: a control signal indicating the start of data terminal ID: a terminal ID for identifying the CATV terminal device 13 at the subscriber's house. Alarm content: a carrier level is below a normal value. Other than operating hours ・ 7 hours or more (continue for a predetermined time or more) ・ Noise level or more ・ ETX: Set a control signal that indicates the end of data.

[0052]

As described above, according to the present invention,
Not abnormal even if the carrier level drops at midnight or early morning, or abnormal if the carrier level drops for a long time, or abnormal if the carrier can be detected but is below the normal level Since the configuration is adopted, it is possible to accurately detect an abnormal decrease in the signal level of the network and automatically notify the center 1 of that. As a result, an abnormality in the signal level of the cable broadcasting network can be automatically detected by the CATV terminal device 13 and notified to the center 1, so that it is possible to perform accurate signal level maintenance of the network.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is a flowchart (No. 1) for explaining the operation of the present invention.

FIG. 4 is a flowchart (part 2) for explaining the operation of the present invention.

FIG. 5 is a flowchart (No. 3) for explaining the operation of the present invention.

FIG. 6 is an operation explanatory diagram of the present invention.

FIG. 7 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 1: Center 2: TV modulator 3: Scrambler 4: Mixer 5: Subscriber telephone network 6: Communication control device 7: Control computer 8: FSK modulator 9: High output amplifier 10: Coaxial network 13: CATV Terminal device 14: TV 18: Signal level detection unit 21: Clock unit 22: CPU 23: Abnormality detection processing 24: Memory 25: Carrier level determination table

Claims (4)

[Claims] 1. A CATV for detecting a signal level of cable broadcasting.
The terminal device for CATV includes a signal level detection unit (18) for receiving a cable broadcast and detecting a signal level of the carrier.
In preparation for 3), when the level of the carrier received by the signal level detection unit (18) of the CATV terminal device (13) is equal to or lower than the normal value and is in the operating time zone, the received signal level is abnormally lowered. CAT characterized by being configured to detect
V terminal device. 2. A CATV for detecting a signal level of cable broadcasting.
The terminal device for CATV includes a signal level detection unit (18) for receiving a cable broadcast and detecting a signal level of the carrier.
In preparation for 3), when the level of the carrier received by the signal level detecting unit (18) of the CATV terminal device (13) is equal to or lower than the normal value and continues for a predetermined time or longer, the received signal level is abnormally lowered. A terminal device for CATV, which is configured to be detected. 3. A CATV for detecting a signal level of cable broadcasting.
The terminal device for CATV includes a signal level detection unit (18) for receiving a cable broadcast and detecting a signal level of the carrier.
In preparation for 3), when the level of the carrier received by the signal level detection unit (18) of the CATV terminal device (13) is less than the normal value and the carrier can be detected, the carrier cannot be detected and the operating time zone In this case, when the carrier cannot be detected, is not in the operating time zone, and continues for a predetermined time or longer, and when either of
Terminal device. 4. When it is detected that the level of the received signal is low, the alarm data having the set content is automatically transmitted to a center or the like for notification. Item 3. A CATV terminal device according to Item 3.