JPH01320888A - Polling system for catv notice broadcast terminal - Google Patents

Abstract

PURPOSE:To avoid unnecessary retry even in case of non-response of partial terminals due to disconnection of a transmission line or the like by changing the number of object terminals to be polled based on discrimination of the presence or the absence of the audio carrier signal outputted from each terminal. CONSTITUTION:In a center equipment 2, the audio carrier signal transmitted through a CATV transmission line 1 is detected by a corresponding audio RF demodulator and audio carrier signal output information is applied to a controller 4. The controller 4 periodically monitors audio carrier signal output information. Terminals for which audio carrier signal output information are absent are not polled because it is judged that power sources are turned off or the transmission line is disconnected in these terminals. Terminals for which audio carrier signal output information are present are polled, and the center equipment 2 selects a CATV notice broadcast terminal and instructs the terminal to receive data and starts data transmission.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a terminal that performs voice announcement broadcasting using a CATV network, and is a polling control method for a terminal that uses a common carrier signal for bidirectional communication with a center device. Regarding the meter.

[Conventional technology]

Conventionally, for polling control of this type of terminal, a specific frequency within the band is allocated as a control signal (one for uplink and one for downlink is allocated because it is bidirectional communication), and this control signal is shared. On the center equipment side, one method is hole-lefting. Then, by polling, one terminal is selected from among the plurality of terminals, and data is exchanged with that terminal.

[Problem to be solved by the invention]

With the conventional polling method described above, inconveniences tend to occur when the terminal becomes inoperable due to a power cut or the like. In other words, if a terminal does not respond when polling is performed, it is difficult for the center device to immediately determine that there is a terminal failure, so polling must be attempted (reconfirmed) several times. It won't happen. Such a trial is necessary because there is a possibility that the data may be erroneous due to noise in the CATV transmission line. In order to perform a retry, the time required for polling must be extended, and therefore, the conventional polling method has the disadvantage that the response of the system is slow.

It is an object of the present invention to provide a polling method for CATV announcement broadcasting terminals that eliminates such drawbacks and can avoid fruitless attempts even if the negative terminal becomes unresponsive due to a power outage or transmission line disconnection. It is in.

[Means to solve the problem]

The present invention is a polling method for performing data communication between a terminal and a center device in an announcement broadcasting system consisting of a plurality of terminals and a center device using a CATV network, and each terminal uses an audio carrier of a different frequency. The center device constantly outputs signals, monitors these audio carrier signals at regular intervals, and changes the number of terminals to be polled based on the determination of the presence or absence of the audio carrier signal.

〔Example〕

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

FIG. 1 shows a configuration example of an announcement broadcasting system implementing the polling method of CATV announcement broadcasting terminals of the present invention, in which n CATV announcement broadcasting terminals T + , T 2 ゜, . . .
'r, is connected to CATV transmission line 1.

Each terminal has an audio RF modulator M1. which forms an audio FM signal. M2. ...9M7, and the frequency of the audio carrier signal is selected differently for each terminal. And each audio RF modulator M + ,
M2. ...1Mo converts the audio carrier signal into C
'Always output to ATV transmission line 1.

In addition, each CATV announcement broadcasting terminal is equipped with a data RF modem D.
,,D2. ..., D, and l, respectively.

On the other hand, the center device 2 includes a terminal audio RF modulator M,
1M2. . . . n audio RF demodulators DM1. DM2. . The center device 2 also includes a data RF modem 3.

A control device 4 composed of a CPU and the like is provided on the center device 2 side, and this control device controls audio RF demodulators DM, D'M2. ..., DM, monitors the audio carrier signal output information outputted by the DM, and controls the polling target.

Next, the operation of this embodiment will be explained.

In the CATV announcement broadcasting terminal, when the power is turned on, the audio RF modulator sends out an audio carrier signal to the CAT ■ transmission line 1 . The center device 2 transmits the audio carrier signal sent via the CATV transmission path 1 to the corresponding audio RF
It is detected by a demodulator and the audio carrier signal output information is added to the control device 4.

The control device 4 monitors the audio carrier signal output information at regular intervals. This cycle may be selected as appropriate depending on the access speed of the terminal side.

Through such monitoring, the terminal determines that the power supply or transmission path has been cut off and does not perform polling on a terminal for which there is no audio input/rear signal output information. In other words, the number of terminals to be polled is changed. This avoids futile attempts.

Polling is performed for terminals with audio carrier signal output information, and the center device 2 selects a CATV announcement broadcasting terminal, instructs the terminal to receive, and starts data transmission. The data RF modem on the terminal side and the data RF modem on the center device side are used to perform bidirectional data communication.

One embodiment of the present invention has been described above, but CATV
Of course, the present invention is applicable regardless of whether the announcement broadcasting terminal is a reception-only terminal or a terminal with a transmission function.

〔Effect of the invention〕

As explained above, the present invention detects the presence or absence of an audio carrier signal output from a terminal, uses this to determine whether or not to perform polling, and enables efficient polling. This has the effect of avoiding useless attempts even if there is no response due to disconnection or transmission line disconnection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an announcement broadcasting system that implements the polling method of the CATV announcement broadcasting terminal of the present invention. 1...CATV transmission line 2...Center device 3...RF modem for data 4...Control device T+~T7...CATV announcement broadcasting terminal M+""
'M-...Audio RF modulator DM, ~DM,
...RF demodulator for audio, ~Dゎ ...R for data
F Modem Agent Patent Attorney Yoshiyuki Iwasa

Claims (1)

[Claims] (1) A polling method for performing data communication between terminals and the center device in an announcement broadcasting system that uses a CATV network and consists of multiple terminals and a center device, in which each terminal uses an audio carrier signal of a different frequency. The center device monitors these audio carrier signals at regular intervals, and changes the number of terminals to be polled based on the determination of the presence or absence of the audio carrier signal. Polling method.