JPH0733501Y2 - Terminal condition monitoring device for one-way CATV system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a one-way CATV system that centrally monitors the status of terminal devices by polling in a one-way CATV system capable of transmitting high-frequency signals only from the center device to the terminal device side. The present invention relates to a terminal status monitoring device of a system.

[Prior Art] Conventionally, in a bidirectional CATV system, a down amplifier and an up amplifier, that is, a bidirectional amplifier is provided in a terminal device such as a main amplifier provided in a coaxial transmission line drawn from a center device. Therefore, status information of the terminal device, such as AC voltage, DC voltage, AGC voltage, and amplifier output level, is returned by polling from the center device and is centrally monitored by the center device.

On the other hand, there is also known a one-way CATV system in which only a downlink amplifier is provided in a terminal device connected to a coaxial transmission line from a center device.

[Problems to be solved by the invention] However, in the conventional one-way CATV system,
Since there is no upstream transmission function that sends high-frequency signals from the terminal equipment to the center equipment, it is not possible to realize terminal status monitoring that returns status information in response to polling from the center equipment, and inspection and maintenance of the CATV system still remains. There was a problem that maintenance was troublesome because it had to be done manually.

The present invention is a one-way system that does not have a high-frequency signal upstream transmission function.
It is an object of the present invention to provide a terminal condition monitoring device for a one-way CATV system that can easily return status information from a terminal device in response to polling of a center device and perform centralized monitoring even in a CATV system.

[Means for Solving the Problem] First, the present invention is directed to a center device 10, a coaxial transmission line 12 drawn from the center device 10, a coaxial amplifier 12 connected to the coaxial transmission line 12, a downstream amplifier 16, an input / output Branch lines are taken out from both sides of the terminals 42 and 44, low-frequency bypass lines connected through low-pass filters 48 and 50, respectively, which cut off high-frequency signals of 70 MHz to 450 MHz and pass only low-frequency signals of 1 MHz or less, and the low-frequency bypass lines. The low-pass filters 48 and 50 provided on the frequency bypass line are rectified and smoothed by inputting the AC power supply signal superimposed on the coaxial transmission line 12 that is provided between the lines of the low-pass filters 48, 50 to drive the downlink amplifier 16. For a one-way CATV system including a plurality of terminal devices 14-1, 14-2, ... . The reference numerals in the drawings of the embodiments are also shown.

In the terminal condition monitoring device of the present invention for such a one-way CATV system, the center device 10 is provided with a downlink 70
Polling means for sequentially repeatedly polling the terminal devices 14-1, 14-2, ... With a high frequency signal using an empty channel within MHz to 450 MHz, and a carrier from the terminal device in response to polling by the polling device. Band (number
(KHz to 1MHz) is provided with reception monitor means for decoding status information of the terminal device returned by a low frequency signal within KHz to 1MHz and displaying an alarm when there is an abnormality, while the terminal devices 14-1, 14 are provided. Each of -2, ... Is provided with means for modulating and returning a low-frequency signal in the carrier band based on the status information when the self-polling by the center device 10 is determined.

[Operation] According to the terminal condition monitoring device of the one-way CATV system of the present invention having such a configuration, the terminal device provided with the downstream amplifier blocks high-frequency signals but passes AC signals for AC power supply. Since the low-frequency bypass transmission line to be set is provided in advance, the low-frequency signal of the carrier band returned from the terminal device in response to the polling from the center device is transmitted from the terminal device connected to the midway coaxial transmission line. Since it can be transmitted to the center side through a low-frequency bypass transmission line for AC power supply and uses a frequency band of 1 MHz or less, the transmission loss is extremely small, for example, about 1 dB / km, and an upstream amplifier is installed on the way. Even if it is not necessary, the center device can obtain a sufficient reception level of the terminal return signal, and the central device can easily perform the centralized monitoring of the state of the terminal device.

[Embodiment] FIG. 1 is a block diagram of an embodiment showing one embodiment of the present invention.

In FIG. 1, 10 is a center device, and the center device 10
A coaxial transmission line 12 is drawn from the coaxial transmission line 12, and the coaxial transmission line 12 includes a status monitor terminal device 14-1 having only a downstream amplifier.
14-2, ... are connected.

A CPU 18 is provided in the center device 10, and a display device 20, a ROM 22 storing a control program, a RAM 24 temporarily storing control data and the like, a voice synthesis output device 26 and an automatic dial device 28 are provided to the CPU 18 by a bus 30. Connected via. In addition, the communication unit 32, RF
A modem 38 and a mixer 40, which are composed of a modulator 34 and a carrier demodulator 36, are provided.

The CPU 18 has a status monitor terminal device 14-1, 14-2, ...
・ A control function as a polling means for sequentially and repeatedly polling and a control function as a reception monitor means for decoding status information returned from the terminal device in response to the polling and displaying an alarm when an abnormality occurs It is provided. The communication unit 32 creates polling data based on the polling control from the CPU 18 and outputs the RF of the modem 38.
Output to the modulator 34. This polling data consists of 3 bytes and consists of a terminal address, command data, and BCC (block check code). The RF modulator 34 FSK-modulates the polling data from the communication unit 32 with frequencies f1 and f2, and further uses an FSK-modulated signal in the downlink direction 70 MHz to 450 MHz.
FM-modulates a high frequency signal of a predetermined empty channel within MHz and outputs it.

The mixer 40 outputs the FSK-FM modulated high frequency signal from the RF modulator 34 to the coaxial transmission line 12, and separates the low frequency signal within the carrier band of several KHz to 1 MHz sent from the terminal side. Is output to the carrier demodulation unit 36. The low frequency signal in the carrier band from this terminal is also FSK-FM modulated on the terminal device side based on the status information, so the carrier demodulation unit 36 demodulates the communication unit 32.
Output to. The status information from the terminal demodulated by the carrier demodulation unit 36 also has a 3-byte structure, and the terminal address,
It consists of command data and BCC. The communication unit 32 performs a parity check based on the BCC of the status information from the carrier demodulation unit 36, and outputs the terminal address and data (status information) to the CPU 18 if the received data is correct.

When the CPU 18 receives status information corresponding to polling from the communication unit 32, it decodes the status information,
If there is an abnormality, an alarm is displayed on the display device 20. In the case of unattended monitoring, the voice synthesis output device 26 and the automatic dial device 28 are activated, and the voice synthesis output device 26 uses the public line as a voice signal to call the preset telephone number through a public line. Like

FIG. 2 shows the status monitor terminal device 14- shown in FIG.
It is an Example block diagram which showed one Example of 1,14-2, ....

In FIG. 2, the status monitor terminal device 14 has an input terminal 42 and an output terminal 44, and a bandpass filter having a pass band of 70 to 450 MHz downstream via a DC cut capacitor C1 following the input terminal 42. 46 is provided, and then the downstream amplifier 16 is provided. The output of the downstream amplifier 16 is 70-
It is connected to the output terminal 44 via a bandpass filter 48 having a pass band of 450 MHz and a DC cut capacitor C2.

Inductance L1 and capacitor before capacitor C1
A branch line is taken out by a low-pass filter 48 composed of C3, this branch line passes through switches SW1 and SW2, and further, a low-pass filter 50 composed of an inductance L2 and a capacitor C4.
It is connected between the capacitor C2 and the output terminal 44 via.
The low-pass filters 48 and 50 cut off high frequency signals of 70 to 450 MHz downstream and pass only low frequency signals of 1 MHz or less.
The number of carrier bands KHz to 1M in parallel with the switches SW1 and SW2
Band-pass filters 52 and 54 that have a pass band of Hz and do not pass AC are connected.

A power supply device 56 is connected between the switches SW1 and SW2 via an inductance L3. The power supply device 56 receives an AC power supply signal superposed on the coaxial transmission line 12, that is, rectifies and smoothes by inputting an AC power supply signal of 30 V at a frequency of 50 Hz or 60 Hz,
In order to drive the down amplifier 16, for example, a power supply voltage of 24V DC is generated.

The switches SW1 and SW2 are turned on and off depending on whether or not 30 V AC is supplied to the front stage or the rear stage. Therefore, the filter
52 and 54 are 50Hz or 60Hz when the switches SW1 and SW2 are off.
The AC power signal is cut off, but the low frequency signal of the carrier band of several KHz to 1 MHz used for the upstream transmission of the present invention is allowed to pass.

On the other hand, since the status information is returned in response to polling from the center device 10, the RF demodulation unit 58 and the carrier modulation unit 60
A modem 62 including a CPU, an I / O 66, a status information buffer 68, and an address setting unit 74 are provided. RF demodulator 58
Is input to the distribution output of the distributor 70 provided at the output stage of the downstream amplifier 16, demodulates the high frequency signal sent from the center device 10 by FSK-FM modulation, and the received data RD is sent to the CPU 6
Output to 4. The CPU 64 determines whether the terminal address and the self-address set by the address setting unit 74 match because the received data RD has a 3-byte structure including the end address, command data, and BCC, and the address match is obtained. At this time, it is determined that it is a self-call, and at this time, a return data format is created from the status information from the status information buffer 68 obtained via the I / O 66, and is output to the carrier modulator 60 as transmission data SD. The carrier modulation unit 60 transmits the transmission data S within the carrier band of several KHz to 1 MHz.
After performing FSK modulation with frequencies f1 and f2 corresponding to D data bits 1 and 0, for example, a frequency signal of 1 MHz is FM-modulated and output. A carrier switch 72 is provided at the output stage of the carrier modulator 60. When the power transmission mode is set by the CPU 64, the carrier switch 72 is turned on to turn on the carrier modulator 60.
Then, the FSK-FM modulated signal from is transmitted to the coaxial transmission line 12 from the input terminal 42 via the low pass filter 48.

Here, the status information stored in the status information buffer 68 includes the AC voltage for the power supply 56 and the power supply.
Environmental data such as DC output voltage from 56, AGC control voltage of down amplifier 16, output level of down amplifier 16, temperature, humidity, etc.,
Appropriate information necessary for terminal status monitoring, such as whether or not there is an emergency power supply operation, is targeted.

Next, the operation of the above embodiment will be described.

First, the center device 10 shown in FIG. 1 creates polling data with different terminal addresses in a predetermined order in the communication unit 32 under the polling control by the CPU 18,
FSK-FM modulation is performed by the modulation unit 34, and the FSK-FM modulation is transmitted to the coaxial transmission line 12 using an empty channel of 70 to 450 MHz in the downlink direction. CPU18 is 1
When the transmission of polling information for one terminal address is completed, a response waiting state is entered.

Each of the status monitor terminal devices 14-1, 14-2, ... Receives a high frequency signal for polling from the center device 10 as shown in FIG. Then, the received data RD is fetched into the CPU 64, and it is determined whether or not the own address and the received terminal address match. Here, if the status monitor terminal device 14-1 matches the self address, the terminal address, data and BCC are sent to return the status information from the status information buffer 68 obtained via the I / O 66.
And send it as carrier data SD to the carrier modulator 60, and the carrier modulator 60 performs FSK-FM modulation as a low-frequency signal in the carrier band on the coaxial transmission path via the carrier switch 72 in the ON state. Return to 12. The response signal from the status monitor terminal device 14-1 using the frequency in the carrier band is the center device.
The signal is separated by the mixer 40 of 10 and given to the carrier demodulation unit 36, demodulated into received data by the carrier demodulation unit 36 and given to the communication unit 32, and after performing a parity check in the communication unit, the terminal address and the data are given. Output to CPU18. The CPU 18 decodes the status information from the terminal in response to the polling obtained from the communication unit 32, and if the status information is abnormal, displays an alarm on the display device 20 to notify the operator of the abnormality.

In the same manner, the status monitor terminal device 14-2 and the subsequent devices are similarly monitored while incrementing the polling address.

If the return signal (upstream signal) from the terminal device is 1 MHz, the attenuation in the 50Ω or 75Ω AF simultaneous cable is about 1.5 dB / Km, which is small, and an upstream amplifier is installed in the upstream transmission path from the terminal device to the center device. Even without it, the terminal device can obtain a sufficient reception level of the return signal.

[Advantages of the Invention] As described above, according to the present invention, the downward direction 70-
The status information is sent back to the center device by a low-frequency signal within a carrier band of several KHz to 1 MHz from the terminal device in response to polling from the center device using an empty channel within 450 MHz. The terminal response signal can be transmitted to the center device through the bypass transmission line for passing the AC power supply, and the attenuation amount is very small because it is the frequency within the carrier band, so an upstream amplifier etc. is required. Even if it is a one-way CATV system that can obtain a sufficient reception level of the terminal return signal at the center device and has only the transmission function of the high frequency signal in the downlink direction, the terminal device can be easily polled from the center device. A system configuration for centralized monitoring can be realized, and maintenance and inspection of a one-way CATV system can be facilitated.

[Brief description of drawings]

1 is a block diagram of an embodiment of the present invention; FIG. 2 is a block diagram of an embodiment of a status monitor terminal device of the present invention. In the figure, 10: center device 12: coaxial transmission line 14,14-1, 14-2: status monitor terminal device 16: down amplifier 18,64: CPU 20: display device 22: ROM 24: RAM 26: voice synthesis output Device 28: Automatic dial device 30: Bus 32: Communication unit 34: RF modulator 36: Carrier demodulator 38,62: Modem 40: Mixer 42: Input terminal 44: Output terminal 46, 48, 52, 54: Bandpass Filters 48, 50: Low-pass filter 56: Power supply 58: RF demodulator 60: Carrier modulator 66: I / O 68: Status information buffer 70: Distributor

Claims (1)

[Scope of utility model registration request] 1. A center device, a coaxial transmission line drawn out from the center device, a down-direction amplifier connected to the coaxial transmission line, and branch lines taken out from both sides of the input / output terminals, and a high-frequency signal of 70 MHz to 450 MHz. And a low-frequency bypass line that is connected through low-pass filters that pass only low-frequency signals of 1 MHz or less and a line provided between the low-pass filters provided in the low-frequency bypass line. A plurality of terminal devices including a power supply device that receives an AC power supply signal superimposed on the coaxial transmission line, rectifies and smoothes the same, generates a DC power supply voltage for driving the down amplifier, and supplies the down power to the down amplifier. In a one-way CATV system composed of and, in the center device, the plurality of terminals are provided with a high frequency signal using an empty channel within 70 MHz to 450 MHz in the downlink direction. When there is an abnormality by deciphering the status information of the terminal device returned by the low frequency signal within the carrier band from the terminal device in response to the polling means for sequentially and repeatedly polling the device Reception monitor means for displaying an alarm is provided. On the other hand, each of the plurality of terminal devices modulates a low-frequency signal in a carrier band with status information when it determines its own polling by the center device, and then the center device A terminal condition monitoring device for a one-way CATV system, characterized in that it is provided with means for returning to the terminal.