JP2577736B2 - Signal transmission method between center and terminal in television co-listening system - Google Patents

Description

The present invention relates to a signal transmission method between a center of a television co-listening system (CATV system) and many terminals, for example, a status monitor and a center of each terminal. This is used when data is transmitted between devices.

(Prior art) When data is transmitted between the status monitor of the terminal of the television co-listening system and the center, each terminal is conventionally addressed, and an address signal (call signal) is transmitted from the center to the terminal to be called, and the terminal is called. Data transmission was performed between the called terminal and the center.

In this case, for example, if the address is 8 bits at the center, the number of addresses can be only 256. For this reason, for example, when the number of the terminals a in FIG. 3 is more than that, even if the terminal is called by a calling signal of one frequency (for example, F1), the maximum is obtained.
Only 256 terminals can be called, not all terminals.

In such a case, a plurality of paging signals (for example, F1, F2, F3, F4) having different frequencies are conventionally transmitted from the center as shown in FIG. 3, and the terminal connected to the distribution line A by the F1 paging signal. Are called by address, and the terminals connected to the distribution line B are called by address with a call signal F2 of F2, and so on.
The terminals connected to C and D are called by calling signals having different frequencies.

(Problems of the prior art) The conventional data transmission method has the following problems.

(1) When the frequency of the call signal increases, the reception frequency of the terminal must be adjusted to the frequency of the call signal. Therefore, terminals having different reception frequencies must be prepared for the frequency of the call signal. Types increase.

(2) When the number of types of terminals increases, the number of types of terminals decreases and the cost of terminals increases.

(Object of the Invention) It is an object of the present invention to enable one type of terminal to transmit data even when the number of terminals is large.

(Means for Solving the Problems) In the present invention, the data transmission method of the television co-listening system according to the first aspect of the present invention, as shown in FIG. Downlink signals F1 to F4 having different frequencies are transmitted to each of the lines 2a to 2d, and in each of the distribution lines 2a to 2d, a down signal having one different frequency is selected from among the down signals F1 to F4 and selected. The frequency-converted downstream signal is converted into a downstream signal F5 of the same frequency by each of the frequency converters 3a to 3d, and the downstream signal F5 is transmitted to each terminal of each of the distribution lines 2a to 2d. The upstream signal R5 is transmitted, the upstream signal R5 is converted into upstream signals R1 to R4 of different frequencies by the respective frequency converters 3a to 3d, and the upstream signals R1 to R4 are transmitted to the center 1. It is a method that did.

The data transmission method of a television co-listening system according to claim 2 of the present invention is the same as the signal transmission method between a center and a terminal in the TV co-listening system according to claim 1, This is a method in which a path line 6 is provided in ~ 3d so that a downstream signal transmitted from the center 1 is transmitted to a terminal through the path line 6 as it is.

(Embodiment) FIG. 1 is a schematic explanatory view of a signal transmission method of the present invention,
FIG. 2 is an internal explanatory diagram of the frequency converters 3a to 3d in FIG.

In FIG. 1, 1 is a head end of a center, 10 is a distributor, 2a to 2d are distribution lines, and 3a to 3d are frequency converters.

The frequency converters 3a to 3d in FIG. 1 have a configuration as shown in FIG. That is, the band-pass filter 4, the downstream signal converter 5, the upstream signal converter 7, the pass line 6, the high-pass filters 8a and 8b, and the low-pass filters 9a and 9b.
It consists of.

In FIG. 1, when downstream signals F1 to F4 having different frequencies are transmitted from the center 1, the downstream signals F1 to F4 are sent to all of the distribution lines 2a to 2d, and the respective distribution lines are transmitted.
Only one of the downstream signals is extracted by the band-pass filter 4 (FIG. 2) in the frequency converters 3a to 3d provided in 2a to 2d. By the way, the frequency converter 3a in FIG.
In the band-pass filter 4 in, the down signal of F1, in the band-pass filter 4 in the frequency converter 3b, the down signal of F2, in the band-pass filter 4 in the frequency converter 3c, the down signal of F3, and in the frequency converter 3d. The bandpass filter 4 extracts only the downstream signal of F4.

The individual downlink signals F1 to F4 extracted by the band-pass filters 4 of the respective frequency converters 3a to 3d are all converted to the same frequency by the converters 5 (FIG. 2) in the respective frequency converters 3a to 3d. It is converted to F5, and the downlink signal F5 is transmitted to each terminal and received by the data transmission terminal (for example, a modem) of each terminal. Each terminal is called by an address determined for each of the distribution lines 2a to 2d.

Since it is necessary to send not only data but also a television signal (TV signal) to each terminal, a pass line 6 is provided in each of the frequency converters 3a to 3d as shown in FIG. A part of the downstream signal (TV signal and F1 to F4) is transmitted to the terminal through the pass line 6 as it is, and the TV signal included in the signal is received by the terminal's television receiver. is there.

The terminal for data transmission of each terminal is designed to receive only the downlink signal F5 frequency-converted by the frequency converters 3a to 3d, and the other downlink signals F1 to F4 and TV signals are used for the data transmission. Not received by the terminal.

Next, all the terminals connected to the respective distribution lines 2a to 2d can send out the upstream signal R5 of the same frequency toward the center 1. The upstream signal R5 sent from the terminal called from the center is the distribution line 2a ~
In the converter 7 (FIG. 2) in the 2d frequency converters 3a to 3d, the signals are converted into any of the uplink signals R1 to R4 of different frequencies and sent to the center 1. As a result, the center 1 can determine from which terminal of the distribution line the received uplink signal has been transmitted.

(Effects of the Invention) The data transmission method of the television co-listening system according to claim 1 of the present invention has the following effects.

(1) Even if the number of terminals increases, all downlink signals from the center can be received by the same terminal, so that the cost of the terminal is reduced.

(2) Since there is only one type of terminal, the cost of the terminal is reduced, and maintenance and management of the terminal are also facilitated.

(3) Even if the number of terminals increases, the configuration between the center and the terminals is simple, so that the implementation is easy and the cost is reduced.

According to the data transmission method of the television co-listening system described in claim 2 of the present invention, not only data but also a television signal can be transmitted from the center to each terminal.
The signal can be received by the television receiver of the terminal.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a signal transmission method of the present invention, FIG. 2 is an internal explanatory diagram of the frequency converter in FIG. 1, and FIG. 3 is an explanatory diagram of a conventional signal transmission method. 1 is a center 2a to 2d is a distribution line 3a to 3d is a frequency converter F1 to F4 is a down signal F5 is a frequency converted down signal F5 is an up signal R1 to R4 is a frequency converted up signal

Claims (2)

(57) [Claims] 1. A down-link signal (F1 to F4) having a different frequency is transmitted from a center (1) of a television co-listening system to each of two or more distribution lines (2a to 2d).
In 2d), a downstream signal of one different frequency is selected from the downstream signals (F1 to F4), and the selected downstream signals are all converted by the respective frequency converters (3a to 3d) into downstream signals (F5 to F5) of the same frequency. ) And frequency-converted to the downstream signal (F5)
Is transmitted to each terminal of each distribution line (2a to 2d), an uplink signal (R5) of the same frequency is transmitted from each terminal, and the uplink signal (R5) is transmitted to each of the above-mentioned frequency converters (3a to 3d). 3d)
Between the center and the terminal in the TV co-listening system characterized in that the signals are converted into upstream signals (R1 to R4) having different frequencies and the upstream signals (R1 to R4) are transmitted to the center (1). Signal transmission method. 2. A signal transmission method between a center and a terminal in a television co-listening system according to claim 1, wherein a pass line (6) is provided in each of the frequency converters (3a to 3d). A signal transmission method between a center and a terminal in a television co-listening system, wherein a downstream signal transmitted from 1) is transmitted to a terminal through a pass line (6) as it is.