JPS6124869B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-way CATV system. In a two-way CATV system, the central control device closely communicates with each viewing subscriber, and the central control device appropriately provides the programs desired by the viewing subscribers, as well as calculating and recording fees associated with the provision. This paper proposes a two-way CATV system whose purpose is to accurately perform program provision operations and smoothly perform program provision operations.

More specifically, we adopted a refresh-type automatic specific channel reception system in our two-way CATV system as a way to smoothly perform program provision operations. This refresh type automatic specific channel reception system is a system in which the receiver is turned off,
This is a method in which when you re-enter the service, you automatically receive a specific free channel, regardless of which channel you were previously receiving.

FIG. 1 shows a two-way CATV system according to the present invention.
To explain with reference to FIGS. 2 and 3, this system is broadly divided into a central control device, a relay transmission network, and a terminal device. As shown in FIG. 1, the central control device consists of the following devices and functions. In the figure, numerals 1 to 19 indicate the elements shown below.

1 Antenna 2 Television signal processor 3 Television studio equipment 4 Multi-channel scramble device 5 Multi-channel television modulation transmission device 6 Stereo audio studio equipment 7 Multi-channel stereo audio FM modulation transmission device.

8 Combining and dividing filter for transmission 9 Central control computer 10 Buffer memory (core memory) 11 Large capacity memory (disk memory) 12 Clock 13 Teletypewriter 14 Communication data input/output device 15 Sending code converter 16 Frequency shift - Keying modulation and transmission device (FSK modulation and transmission device) 17 Phase shift keying reception and demodulation device (PSK reception and demodulation device) 18 Response signal code converter 19 Program software for central control unit Multi-channel television modulation and transmission device 5 and FM modulation transmission device for multi-channel stereo audio 7
is a device that converts local programs into signals suitable for the CATV frequency band level and sends them out in order to serve each subscriber via a CATV transmission line.

The television studio equipment 3 and the multi-channel television modulation and transmission device 5 can be devices that transmit free programs on specific channels such as program introductions and local government announcements in addition to paid programs.

The transmission coupling and splitting filter 8 is a device that superimposes or separates various signals transmitted through the CATV transmission cable.

Central control computer 9, buffer memory 1
0, large-capacity memory 11, clock 12, and teletypewriter 13 are central control units for data communication functions, and have the function of processing data obtained from each subscriber. Pre-given software
It is a device that efficiently performs various tasks such as communication control, data collection, data aggregation, billing, etc. with each subscriber according to Program 19, and the information contained in the response signal from each subscriber. This is a device that calculates fees based on the usage status of each terminal device. The PSK reception demodulator 17 and response signal code converter 18 are response signal receivers that receive response signals from each terminal device and transmit them to the computer 9.

In addition, the relay transmission network generally includes a main line 22, a trunk line 23, a branch line 24, and a distribution line 2, as shown in FIG.
5. Consists of lead-in line 26.

Next, referring to the terminal device, the terminal device is the in-home device of each subscriber in this system, and an example of the terminal device consists of the following devices as shown in FIG. Reference numeral 32 in Figure 3
The elements indicated by 45 to 45 respectively represent the following elements.

32 Coupler 33 Downlink signal receiving device (FSK receiving device) 34 Terminal signal processing device 35 Address register unit 36 Upstream signal transmitting device (PSK transmitting device) 37 Electronic tuning converter 38 Image control device (descrambler) 39 Auxiliary converter 40 Television receiver 41 Power sensor 42 Channel selection device 43 Key switch 44 Sensor 45 Subscriber response device ``electronic tuning converter'' The electronic tuning converter 37 of the terminal device is capable of controlling the television for 35 channels transmitted from the central control device. This is a device that selects a desired channel to receive from television signals (TV signals) and converts this TV signal into a specific channel that can be received by the television receiver 40. This device is installed in the fourth
Description will be given based on the embodiment shown in the figure.

98 is an input band pass filter (hereinafter referred to as input BPF)
99 is a first frequency converter, 100 is a first local oscillator, and 101 is a helical band pass filter (hereinafter referred to as helical BPF). A first frequency converter to be selected is configured. Further, 102 is a second frequency converter, 103 is a second frequency converter, and 103 is a second frequency converter.
The local oscillator, 104 is an output band pass filter (hereinafter referred to as output BPF), and these are the first
TV for one channel selected by the frequency conversion section
A second frequency conversion unit is configured to convert the signal into a specific channel that can be received by the television receiver 40. 105 detects the frequency deviation of the TV signal;
An AFC circuit 106 that outputs a control voltage according to the deviation is an AFC control circuit that detects a change in the output voltage of the channel selection device 42 at the time of channel switching and temporarily stops the operation of the AFC circuit 105.

According to this configuration, if you want to select a channel you want to receive among the 35 channels of TV signals that have passed through the input BPF 98, you can set the desired channel with the channel selection device 42, and then
A voltage corresponding to this channel is set in the channel selection device 42. Channel selection device 42
The voltage set at
A certain oscillation frequency f _L1 is obtained. Assuming that the frequencies of the 35 channels of TV signals transmitted from the central control unit are f ₁ , f ₂ , ..., f ₃₅ , these frequencies that have passed through the BPF 98 are converted to the first frequency converter 99 in the first frequency converter 99 . It is mixed with the local oscillation frequency f _L1 and converted into an intermediate frequency including two frequency components as shown by the following equation.

Out of the intermediate frequency components in equation (4), only one frequency with a sum component is taken out by the helical BPF 101 and applied to the second frequency converter 102. Even though the input stage of the first frequency converter 99 is of a non-tuned type, a desired channel (frequency f _o ) can be extracted by the helical BPF 101 .
Equation (5) is the intermediate frequency after passing through the helical BPF 101.

f _o +f _L1 ...(5) In the second local oscillator 103, a constant frequency f _L2 is oscillated, and this frequency f _L2 and the intermediate frequency (f
_o +f _L1 ) in the second frequency converter 102. This mixed second intermediate frequency component includes two frequency components as shown in equation (6),
Outputs only the difference frequency component of this frequency component
It is possible to extract the frequency from the BPF 104 and supply a frequency corresponding to a specific channel (for example, channel 2) of a general television receiver 40. Equation (6) represents the second intermediate frequency component, and Equation (7) represents BPF1
04 and extracts the difference frequency component.

(f _o + f _L1 ) ± f _L2 ... (6) (f _o + f _L1 ) - f _L2 = constant (2 channels of general television) ... (7) On the other hand, the AFC circuit 105 uses this equation (7). Amplifying the frequency component of a specific channel (for example, channel 2) of the television receiver 40 shown in
The AFC voltage is obtained by detection with a frequency discriminator,
This AFC voltage is superimposed on the channel selection voltage output from the channel selection device 42, and
The oscillation frequency of the first local oscillator 100 is automatically controlled so that the desired channel can always be received in the best condition.

Further, the AFC control circuit 106 constantly monitors the channel selection voltage output from the channel selection device 42, and immediately upon detecting a change in the channel selection voltage, changes the AFC voltage of the AFC circuit 105 to the first local oscillator. It operates so as not to output for a short period of time until 100 operates stably. After this channel switching is completed, the AFC circuit operates normally and controls the oscillation frequency of the first local oscillator 100 so that the desired channel can always be received in the best condition.

With this configuration, this device has a simple circuit configuration with a small number of stages, does not malfunction due to AFC pull-in, is always stable, and can easily obtain image control signals (15750Hz), making it extremely effective. It functions as an electronic tuning converter.

"Power Sensor" The power sensor 41 is a device that detects whether the television receiver 40 in the terminal device is powered on. FIG. 5 shows an example of this.

190 is a rectifier diode, 191 and 192 are voltage dividing resistors, each connected in series, and connection points A and B.
Furthermore, a capacitor 193 is connected in parallel to the resistor 192, thereby configuring a DC power supply. 195 is the relay coil, capacitor 19
4 are connected in parallel and connected to both ends of the capacitor 193 via the collector and emitter of a transistor 196. The base of transistor 196
There is a resistor 197 and a diode 19 between the emitters.
A parallel circuit of 8,199 and a diode 200 is connected through a resistor 201. Power to the television receiver 40 is led from the connection point A mentioned above and the connection point C in the figure. Diode 190, resistor 19
1,192 and a capacitor 194 supplies a sufficiently smoothed DC voltage to the circuit. When the power switch of the television receiver 40 is closed, a half cycle of alternating current flows through the diodes 198 and 199, generating a forward voltage.
In the next half cycle, alternating current flows through the diode 200 and a forward voltage drop occurs, but these forward voltages have little effect on the alternating current line, such as ripples. In the half cycle when the current flows through the diodes 198, 199, the diodes 198, 19
The forward voltage developed across transistor 9 is
Since 96 is made conductive, as a result, relay coil 1
Current flows through 95, activating the relay.

On the other hand, during the half cycle in which current flows through the diode 200, a reverse bias is applied to the transistor 196, so the charge stored in the capacitor 193 starts discharging through the relay coil 195, and as a result, the relay maintains its operating state. become. Thus, as long as the power switch of television receiver 40 is closed, the relay remains operative. Even if the power switch of the television receiver 40 is opened, the television receiver 4
Since the preheater current flows through 0, the power
A small amount of current may also flow through the diodes 198 and 199 of the sensor 41, causing the transistor 196 to operate. To prevent this malfunction of the transistor 196, a resistor 1 is connected to the diodes 198 and 199.
97 are arranged in parallel.

When the preheater current is flowing, that is, when a small current is flowing through the diodes 198 and 199, the equivalent resistance R of the diodes 198 and 199 is
_S has a large resistance value. Therefore resistance 19
If the resistance value of transistor 7 is set to a value smaller than the equivalent resistance R _S , the bias of transistor 196 will be the voltage across resistor 197, so transistor 19
6 is not conductive.

Conversely, when the power switch of the television receiver 40 is turned on, the diodes 198 and 19
Since the current flowing through diodes 9 is a large current, the equivalent resistance R _L of diodes 198 and 199 is smaller than that of resistor 197. Therefore, the bias of the transistor becomes the voltage across the equivalent resistance R _L and the transistor 196 becomes conductive.

In other words, the resistance that satisfies the relationship R _S > R ₄ > R _L
If R ₄ is selected, the power sensor 4
1, and when the current is small, the transistor 1
96 malfunctions are prevented.

For example, to prevent the power sensor 41 from operating below 20 watts, if the forward voltage of one diode V _D =0.7 volts and the AC power supply voltage E is 100 volts, then the current I _D flowing through the diode is I _D ≒20/E=20/100=0.2 [ampere]. Therefore, the equivalent resistance of one diode R
_S1 is R _S1 ≒ V _D / I _D = 0.7/0.2 = 3.5 (ohm), and since diodes 198 and 199 are connected in series, it is twice the equivalent resistance R _S1 of one diode, That is, since R _S =2R _S1 , the resistance 197 only needs to be about 7 ohms. In reality, the value is set to be even smaller than 7 ohms, taking into account the current phase and the diode flow angle. As explained above, this power sensor 41 has a simple circuit configuration and can detect whether the television receiver 40 is powered on or not without any modification, and even if the preheater current is flowing. No malfunctions. Further, the power supply line and the power sensor output can be electrically isolated.

Next, a refresh type automatic specific channel reception system will be explained. In this system, when the power of the television receiver 40 is turned off and then turned on again, a specific free channel is automatically received regardless of which channel was previously received. The programs on this specific channel include content such as public relations and program introductions. Once the television receiver 40 is powered off, that information is communicated to the central controller via the power sensor 41. The channel selection device 42 basically consists of n DC voltage generators that can be selected from the outside with a manual switch, a specific DC voltage setting device for receiving the specific channel, and an analog switch. It is connected to a tuning converter 37 and a terminal signal processing device 34. An example of the configuration of this channel selection device 42 is shown in FIG.
202 is a manual switch selected and operated by the user, and according to the selection, a circuit 203 including n DC voltage generators generates a corresponding voltage. This voltage is applied to one input of analog switch 205. The analog switch 20
5 can be considered as a switch having two inputs, one output, and two control inputs specifying which of the two inputs is connected to the output. Further, another input of the analog switch 205 is supplied with a predetermined voltage from a specific channel receiving DC voltage setter 204 that generates a DC voltage for receiving the specific channel. Analog switch 205 receives, at its control input, a signal, which will be described later, from terminal signal processing device 34 and a switch switching operation signal from manual switch 202. analog switch 2
05 is a DC voltage setter 204 for receiving a specific channel according to a signal from the terminal signal processing device 34.
The voltage from the circuit 203 is connected to the output, and in response to the switch operation signal of the manual switch 202, the voltage from the circuit 203 is connected to the output. The output of analog switch 205 is connected to terminal signal processing device 34 and electronic tuning converter 37. The central controller turns off the power switch using the power sensor 4.
1, it instructs the terminal signal processing device 34 to have the analog switch select the DC voltage for the specific channel and apply it to the electronic tunable converter 37 (more specifically, the first local oscillator 100) in the next polling. . Terminal signal processing device 3
4 switches the changeover switch 205 to the specific channel reception DC voltage setting device 204 in response to this instruction. As a result, when the television receiver is turned on again, the specified free channel is automatically received. If the subscriber wishes to view a program other than this specific channel from the beginning of the next reception, he can select it using the manual switch and then turn on the power switch. In this case, one of the n DC voltage generators is selected and applied to the electronic tuning converter 37 and also transmitted to the terminal signal processing device 34.

Therefore, this refresh type automatic specific channel reception system has the advantage of being able to broadcast regional publicity information and program previews, regardless of each program.

[Brief explanation of the drawing]

1 is a schematic diagram mainly showing a configuration example of a central control device, FIG. 2 is a schematic diagram mainly showing a configuration example of a relay transmission network, FIG. 3 is a schematic diagram mainly showing a configuration example of a terminal device, and FIG. 4 is a schematic diagram mainly showing a configuration example of a terminal device. 5 is a block diagram showing the structure of an electronic tuning converter, FIG. 5 is a circuit diagram showing one structure of a power sensor, and FIG. 6 is a block diagram showing an example of the structure of a channel selection device. ...central control unit, ...relay transmission network, ...
...Terminal device, 3...Television studio equipment, 9...
... Central control computer, 33 ... Downlink signal receiving device, 34 ... Terminal signal processing device, 40 ... Television receiver, 41 ... Power sensor, 42
...Channel selection device.

Claims (1)

[Claims] 1 A central control computer consisting of a central control unit, terminal devices, and a relay transmission network that connects these, where the central control unit controls the entire system and performs sequential data communication by polling the terminal devices according to a predetermined software program. , a communication data input/output device that mediates data communication between this computer and the terminal device, a device that sends instructions from the computer to each terminal device, and a device that receives response signals from each terminal device and transmits them to the computer. A response signal receiving device, a device that calculates fees based on the usage status of each terminal device included in the response signal, and a device that transmits free programs on specific channels such as program introductions and local government public relations in addition to paid programs. A downlink signal receiving device in which each terminal device receives communication data from the central control device, and a terminal signal processing device that operates the terminal device according to instructions included in the received signal and transmits the status to the central control device. A device 34;
It has n DC voltage generators 203 that correspond to n channels including the channel broadcasting the pay program and can be selected by a manual switch, and a DC voltage setter 204 for receiving a specific channel that provides the free program. It includes a channel selection device 42 and a power sensor 41 that detects the on/off state of the power of the television receiver, and when the power of the television receiver is turned off, the power sensor detects that the power of the television receiver is turned off. The terminal signal processing device 34 not only transmits the output of the channel selection device to the central control device via the terminal signal processing device 34, but also sends the output of the channel selection device from the DC voltage generator 203 corresponding to the channel just received. When switching to the DC voltage setting device 204 for receiving a specific channel and turning on the power of the television receiver again, the electronic tuning converter is tuned by the voltage from the DC voltage setting device 204 for receiving the selected specific channel. Features a two-way CATV system.