JPS6065688A - Catv device - Google Patents

Abstract

PURPOSE:To prevent effect on other terminal device even if any of terminal devices is failed by controlling the stop of a data carrier to a center from a terminal device by an instruction signal from the center. CONSTITUTION:When a carrier stop instruction from the center (not shown) enters a data processing circuit 40 via an HPF 29 and an FSK receiver 38, after a microcomputer in the circuit 40 confirms the address, a carrier frequency of a carrier oscillating circuit 47 is switched. As a result, a BSK modulator is not operated and a data from a terminal device is not outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a CATV system in which a center and a terminal device are connected by a bidirectional transmission line.

Conventional configurations and their problems In recent years, centers and terminal devices have been connected using coaxial cables or optical fiber cables, and video signals and necessary data signals are sent from the center to the terminal devices, and from the terminal devices to the center. So-called two-way CATV devices that transmit necessary data signals such as video request data have been developed.

Without further ado, a conventional example of such a CATV device will be explained.

FIG. 1 shows an outline of the basic configuration of a CATV device, and FIG. 2 shows a configuration of a terminal device used therein.

In FIG. 1, reference numeral 1 denotes a line controller on the center side, which controls terminal devices. 2 is an FSK modem transmitter, and 3 is a PSK modem receiver, which belong to the center navel end. 4 is a duplexer 1.5, 6, 7 is a bidirectional line amplifier, 8°9 is a distributor, 10, 11 is a converter for each terminal device, 1. ,,． 2 and 13 are TV cents of each terminal device.

When the line controller 1 sends a data signal including an address designation command for specifying a specific terminal device, this command is FSX-modulated by the FSX modem transmitter 2, and along with the video signal, the duplexer 4 and the bidirectional line Amplifier 5, 6,
It is transmitted via distributors 8, 9 to terminal converters 10.11. Instructions entered into the terminal converters 10, 11 are read by their microcomputers, and only the terminal converter having the approximate address executes the instruction. The converters 10 and 11 perform PSK modulation on data such as whether or not the process is being executed and the status of each terminal converter 10, 11, and return a -I data signal to the center. The upstream data signal passes through distributors 8 and 9, bidirectional line amplifiers 5 and 6, and distributor 4, is demodulated by PSK modem receiver 3, is input to line controller 1, and is displayed on the display of the line controller. .

FIG. 2 shows the CATV controller 7Z-10 of a conventional terminal device.
11 shows a block diagram of No. 11. In Figure 2, 1
4 is a forward signal filter (HPF), 1
5 is the ronokusufu for the rising signal, Iruri (LPF), 1
6 is a band pass (BPF), 17 is a filter, 18 is a channel selection control circuit, a single demodulation circuit, 20 is a descrambler, 21 is an iJ RF modulator, and 22 is an output path for FSK signal. Filter (BPF), 23 is FS
The K receiver 124 is a data processing circuit, 25 is a carrier oscillation circuit, 26 is a PSK modulator, 27 is a PSK output amplifier, and 28 is a PSK signal overpass filter (BPF).

Commands such as address designation sent from the line controller 1 are FSX-modulated by the FSX modem transmitter 2, passed through the duplexer 4, bidirectional line amplifiers 5, 6° distributors 8, 9, and then passed through the terminal converters 10, 11. is input. The code signal of the instruction that entered the terminal converters 10 and 11 is sent to the HPF 14.
．． FSX receiver 23 through BPF16°BPF22
The signal is demodulated and enters the data processing circuit 24. The address of the command input to the data processing circuit 24 is confirmed by the microcomputer in the data processing circuit 24, and the terminal converter 10 determines whether or not the command has been executed.
11 is sent to the PSK modulator 26. The PSK modulator 26 operates only when the SD multiplied signal is present, since the data SC output from the data processing circuit 24 becomes No.1/Bell. The carrier oscillated by the SD double signal carrier oscillation circuit 25 is PSK modulated by the PSK modulator 26, amplified by the PSK output amplifier 27, and then passed through the BPF 28 and LPF 15 to become a converter output.

However, the above configuration has the disadvantage that if the carrier of the malfunctioning terminal converter becomes unavailable due to a malfunction of the terminal converters 10 and 11, the data of the normal terminal converter will be destroyed. .

OBJECTS OF THE INVENTION The present invention provides a device that can eliminate such conventional inconveniences and ensure transmission of upstream data signals from other terminal devices even if there is a failure on the terminal converter side. It is.

Structure of the Invention The present invention is characterized in that two types of frequencies are provided for the uplink oscillation circuit, and a means is provided that allows the line controller to designate and stop these two carrier frequencies.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows a block diagram of a terminal converter used in a bidirectional CATV apparatus according to an embodiment of the present invention.

In Figure 3, 29 is an HPF that passes down signals of 50 or higher, and an LP that passes up signals of 30 or less.
F, 31 is BPF for 7311!15 FSK signal, 3
2 is a tuner, 33 is a tuning control circuit, 34 is a demodulation circuit,
35 is a descrambler.

36 is an RF modulator. 37 is a BPF that passes the FSX signal of 73M1lH, 38 is the FSK receiver-13
9 is a NAND gate and a 40-digit data processing circuit. Still, 41 is a PSK modulator, 42 is a carrier switching driver, 43.44 is a diode, 45 is a resistor, 4
6 is an AND gate, 47 is 2 for upstream data signal E5
hllz and 26 L (h carrier oscillation circuit, 48
is a PSK output amplifier, 491rJ, and a BPF for PSIC signals that passes only 24 to 251h.

Downward commands such as address designation from the line controller 1 that reach the inputs of the converters 10 and 11 are sent to the HPF 29.
．． It passes through BPF31 and BPF37 and enters the FSXS plane 38, where it is converted into an IF multiplied signal (1o, 7oboro),
FSK demodulation is performed.

At this time, if the IF level is 48dB7z or higher, FSK
The output DM of the differential amplifier in the receiver 38 becomes high level, and is inputted to the NAND gate 39 together with demodulated data RD, and then inputted to the data processing circuit 4o. When the IF level is lower than 4sdBμ, I)M becomes low level, the output of NAND gate 39 is high level, and demodulated data is not output. The downlink command (d) that entered the data processing circuit 40 is checked by the microcomputer, and data SD indicating whether the command is effective or not and the status of the terminal converter is sent to the PSK modulator 41.For example, the carrier frequency of the carrier oscillation circuit 47 is 25. When the data processing circuit 40
C8#1 is outputted at high level, and csa2 is outputted at low level. The diode 43 and the conductive diode 44 are in a non-conductive state, and the signal SCB is at a high level.

The opposite is true for 26-meter oscillation. Since the SCA reaches a high level only when the upstream data SD is output from the data processing circuit 40, the SC signal is output at the same timing as the SCA, and the SD multiplied signal enters the PSK modulator 41. The PSK modulator 41 operates only when the SC is at the blank level. PSK modulator 41
The upstream data PSK modulated by PSK output amplifier 4
It passes through a BPF 37 and an LPF 30 with a ratio of 8.24 to 25, becomes a converter output, passes through the main line and head end, and is displayed on the line controller's display.

When a command to stop the addressed carrier from the line controller enters the data processing circuit 24, the data processing circuit 2
After the microcomputer 4 confirms the address, it sets C3s1 and C8#2 to low level. At this time,
Diodes 43 and 44 are in a non-conducting state, and SCB is at a low level, so SC and SCA are at a low level, and the PSK modulator is in main operation, and no upstream data is output from the terminal converter. .

Effects of the Invention As described above, according to the present invention, uplink carriers can be stopped from the line controller, so even if the carrier is disconnected from a specific terminal, data can be recovered normally by switching carriers. Therefore, it is very effective for maintenance.

[Brief explanation of the drawing]

1 and 2 are block diagrams of a conventional CATV device, and FIG. 3 is a block diagram of a CATV device according to an embodiment of the present invention. 29-, /-, Ihas filter, 30...Low pass filter, 31 Band pass filter, 32...Demodulation circuit, 35 Ter scrambler, 36--RF monitor, 37...Band pass filter, 38 FSK
V shifter, 39-NAND gate, 40 ・Data processing circuit, 41...PSK modulator, 42 Carrier switching driver, 43.44...Diode, 4
5 Resistor, 46 ・AND gate, 47 ・Carrier oscillation circuit, 48 ・PSK output amplifier, 49 Bandpass filter.

Claims (1)

[Claims] A bidirectional transmission line is configured to transmit video signals and necessary data signals from the center to the terminal device, and to transmit necessary data signals from the terminal device to the center, and instructions transmitted from the center. A CATV device configured to control the stop of an upstream data carrier for transmitting data signals from the terminal device to the center using a signal.