JP2591231B2 - Bidirectional CATV terminal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a CA of a CATV system that performs two-way data communication.
It relates to TV terminals.

[Conventional technology]

Conventionally, bidirectional data communication in this type of CATV system adopts a method in which a terminal receives and analyzes a data signal of a specific frequency sent from the center, and sends response data from the terminal to the center as necessary. doing. In the level measurement, a level of a specific frequency, for example, a pilot frequency is measured, and the level is returned to the center to detect whether or not the level value is normal at the center.

FIG. 2 shows an example of the conventional system, and its outline will be described. In FIG. 2, a downstream signal including a pilot and a video carrier is input from a CATV line 1 to a duplexer 2 of a CATV terminal, and the split signal is sent to a tuner 3, a data carrier extraction filter 8, and a pilot filter 13, respectively. Is output. At this time, the channel 3 selects a channel designated by the microprocessor 6 and outputs an IF signal. The IF signal is detected by a video detector 4 and an audio detector 5, respectively, and output as a baseband television signal and an audio signal.

In addition, the data signal is a data carrier extraction filter 8.
, And is received and analyzed by the data signal demodulation unit 7. When a response is required, the data is transmitted to the center via the data signal modulator 9, the amplifier 10, the duplexer 2, and the CATV line 1.

On the other hand, the downstream pilot signal is input to the pilot filter 13 from the duplexer 2, detected by the pilot level detector 14 as a level, processed as a data value by the microprocessor 6, and then sent to the data signal modulator 9, the amplifier The data is transmitted to the center via the unit 10.

[Problems to be solved by the invention]

When the level is measured by the center specified by the above-mentioned conventional data communication, the pilot frequency is often measured. Normally, a pilot is often provided with one wave at a high frequency in the transmission band, and it is not possible to determine whether the characteristics of the wide-band transmission path is normal only by measuring the level of the pilot, and it is necessary to measure the entire band again with a measuring instrument. . Also, when the pilot signal has two or more waves, whether the deviation state of the frequency characteristic of the transmission path can be detected respectively,
It is necessary to provide a dedicated filter or the like, and there is a problem in that it is expensive.

[Means for solving the problem]

In order to solve such a problem, the bidirectional CA of the present invention is used.
The TV terminal has a function of selecting a designated channel sent as control data from the center, providing level detecting means for measuring the video level and the audio level, and transmitting the measured level value to the center as a data signal. doing.

[Action]

Therefore, according to the present invention, it is possible to easily measure the level of the channel specified by the center without using a special filter.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of a bidirectional CATV terminal according to the present invention. This embodiment differs from the conventional example shown in FIG. 2 in that an audio level detecting section 11 and an image level detecting section 12 for respectively measuring an audio carrier level and an image level of a channel designated by a center are provided. The level value measured at 12 is
And the level values are sent as data signals to the center via the data signal modulator 9, the amplifier 10, the duplexer 2, and the CATV line 1. The same reference numerals in the drawings indicate the same or corresponding parts.

According to the configuration of the above embodiment, the downstream carrier signal is CATV
The signal is input from a line 1 through a duplexer 2 to a tuner 3 and a data carrier extraction filter 8. When the microprocessor 6 sends channel selection data to the channel 3, the channel 3 tunes to the designated channel. For this reason, the tuner 3 outputs an IF signal, and the IF signal is detected by the video detector 4 and the audio detector 5, respectively, and outputs a video signal and an audio signal. As a result, after the audio detection unit 5 extracts the audio carrier, the audio detection unit 5 sets the audio level to the audio level detection unit 11, and the level detection unit 11 exchanges the audio carrier for the level value.
The level value is held by the microprocessor 6. After extracting the video carrier, the video detector 4 detects the carrier by the video level detector 12 and measures the level by the microprocessor 6. As a result, the measured level can be sent to the center via the data signal modulator 9, the amplifier 10, and the duplexer 2 as a data value.

Note that a variable equalizer for downlink is provided in the circuit of the above embodiment, and when the measured value of each channel has a deviation from the reference value, it can be adjusted.

〔The invention's effect〕

As described above, the present invention makes it possible to measure the level of a specified channel at a center without using a special filter by measuring the level of a video and audio carrier signal selected by a channel. The level status of each channel can be measured for each trunk line and each terminal, which has the effect of improving maintenance efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of the prior art. 1 ... CATV line, 2 ... duplexer, 3 ... channel, 4
... video detector, 5 ... audio detector, 6 ... microprocessor, 7 ... data signal demodulator, 8 ... data carrier extraction filter, 9 ... data signal modulator, 10 ... amplifier, 11: Audio level detector, 12: Video level detector.

Claims (1)

(57) [Claims] 1. Bidirectional data communication between a center and a terminal
In the CATV system, the terminal is provided with level detecting means for measuring the video and audio carrier levels of the channel specified by the center, respectively, and the measured level value is transmitted to the center as a data signal. Two-way CATV terminal.