JPS6054584A - Bidirectional cable television controlling and transmitting device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a device for controlling the distribution of television signals in a CATV type distribution device.

[Technical background of the invention and its problems]

Television distribution equipment usually consists of a head end for providing a television signal and a tree-shaped transmission medium, usually in the form of a coaxial cable main link with branch feeders. Distribution splitters are connected to the feeders, and subscriber drops are connected to each distribution splitter. The subscriber's television set is connected to the subscriber drop. Traditionally, such distribution devices have been unidirectional. That is, a head collects television signals for distribution and transmits them on a receiving television channel through a transmission medium to a subscriber's receiver. In recent years, bidirectional distribution devices have been installed in anticipation of additional services.

The transmission medium was widely used: paper using coaxial cables. Coaxial cables have a transmission band of up to approximately 300 MHz and can carry 35 or more television channels. Standard television reception 12 on the machine
A VEF tuner that accommodates channels and an Ota tuner that can theoretically receive 70 channels are provided. However, since the CATV system can only transmit the OH7 frequency with very low quality, it is necessary to convert the JHF television channel to an intermediate channel between 6.7 channels or 13 channels or more before transmitting it via cable. is normal. All of those channels are in the VHF band.

To receive these intermediate and higher frequency band signals, special converters must be used to interface between the transmission medium and the television receiver. The converter converts all received frequencies into one channel, typically two or three channels. However, it may also be converted to the OHF band.

The converter is externally connected to the television receiver. In some receivers, the converter may be incorporated during the receiver's manufacture.

For supplementary television services such as pay television, video text, etc., there is little control over the converter connected to the subscriber's receiver.

This limits the ability to detect unauthorized use of such services. It is also costly to discontinue the provision of services. This is because a technician must go to the location where the service thief belongs to the distribution divider box, find the service thief, and disconnect the wiring. Furthermore, a large portion of the provision of services to subscribers is under the control of the subscribers themselves.

Since the decoder box is physically installed in the subscriber's home and is easily manipulated, even if a different television channel is provided, the decoder box will be stolen to some extent by the subscriber.

SUMMARY OF THE INVENTION In the present invention, the channel converter is placed under the direct control of the cable system operator.

The converter is not installed in the subscriber's home and only the specific channels selected by the subscriber are sent to the subscriber's receiver via the subscriber's drop.

Furthermore, the type of service can also be determined.

Thus, even if a subscriber requests a certain service to which he is not entitled, that service will not be provided to the subscriber. At the will of the system operator, the service can be terminated under signal control, or the service can be extended if desired. The device can also provide an indication to the operator of which channels have been selected, making it easier to calculate usage fees for a particular service, obtain accurate usage data, etc. Additionally, the device of the present invention allows the subscriber to communicate directly with the head end of the device, facilitating requests for services such as interactive video, visual data type services, pay TV channels, gaming competitions, home computer services, etc. Become. Furthermore, since the converter is not installed in the subscriber's house, there is no possibility of manipulation, theft, or destruction by the subscriber. The device according to the invention also makes it possible to send special channels to subscribers with special contracts.

In the present invention, a subscriber's distribution terminal is connected to a transmission medium to serve a group of subscribers. A plurality of television converters are provided within the distribution control terminal. The local oscillator within each converter is controlled by a microprocessor. A microprocessor establishes selected channels from the multi-channel television signal received from the transmission medium. The output of each converter is connected to a subscriber drop. The drop is connected to the subscriber's television set.

Each subscriber has a control signal generator. This control signal generator is preferably in the form of a hand-held push-button control box. When the channel selection button is pressed, a control signal is generated.

The control signal is processed by the subscriber's terminal and then
The data is sent to the microprocessor of the distribution terminal via the drop. The microprocessor receiving the control signal causes the channel to change by controlling the frequency of the local oscillator of the associated transducer.

The subscriber's local terminal is also connected to the transmission medium and, when polled, receives signals from the head end that are stored in the memory of the head end. Those signals provide data for a questionnaire stored in the microprocessor's memory. These data enable or inhibit control of the converter when a service request or channel change signal is received from the subscriber terminal. Additionally, the head end can ball a local terminal. The local terminal itself can store information about which channel has been selected by the subscriber. Additionally, the local terminal can store requests for service signals provided by the subscriber control signal generator. These service signals must be provided from the head end, and include hito data information and the like.

and (television remote?h1) control equipment includes a VHF transmission medium, a central control unit including a television signal head end, and a digital control unit for transmitting and receiving digital control signals from the central control unit to the transmission medium. and a model for coupling a television head end and a digital control device to a transmission line. At least one subscriber distribution terminal is connected to the transmission medium. a plurality of television converters for receiving and outputting one channel of television channels; a first controller for controlling the channel output from each converter; and a plurality of subscriber drops; a device for receiving a television request signal from each subscriber drop; the subscriber distribution terminal providing a signal to the first controller for controlling the channel output in response to receiving the request signal; and a second controller for applying digital control signals to the transmission medium. At least one subscriber terminal is connected to two corresponding subscriber drops, which subscriber drops are connected to the The subscriber terminal has a connected television terminal, a control signal generator for generating a television channel request signal, and a device for combining the television channel request signals into one subscriber drop. When a television channel request signal is generated at , the converter, under control of the first controller,
One television signal can be added to one subscriber drop.

According to the invention, the invention comprises a central station, a plurality of subscriber distribution terminals, and a tree-type transmission device connecting the central station to each of the distribution terminals. each central office and each distribution terminal;
Each subscriber terminal includes a mounting for transmitting and receiving digital signals, so that data from each subscriber terminal can be communicated to the central office, which central office is connected to a plurality of separate and apparatus for generating for each subscriber terminal a table of channels to which the terminal is accessible, each said subscriber terminal having a television a terminal and a device manually operable for specifying one requested television channel; and a device for generating a digital channel request signal in dependence on the requested channel; A subscriber distribution terminal includes a plurality of television converters, each f, connected to a respective subscriber drop for transmitting a television channel to a respective terminal, and a plurality of television converters connected to said digital channel request signal. sends a digital signal (repeatedly) to each subscriber terminal, receives from the central office the table of channels accessible by the terminal and stores the table, and transmits the request signal to each subscriber terminal. a bi-directional device, comprising: a micro-transducer device configured for comparison with a table; and a device for controlling each transducer to provide the required accessible channel to the respective terminal. A cable television control and transmission device is obtained.

The invention includes parallel-serial bit transmission, microprocessor and computer equipment, polling techniques, etc.
Digital transmission devices such as those using the DEI-1 format are assumed to be well known to those skilled in the art.

The digital transmission device used in the present invention should use the DB,-1 protocol. However, this is not mandatory. In the DS-1 protocol, data signals are typically transmitted at 1.544 M pits per second. The bits are divided into 8000 frames. An l frame consists of 192 data bits and one frame bit. 8000 frames are transmitted per second.

Each frame consists of 24 time slots.

Each time slot is 8 bits long. Thus, each time slot forms a channel of 64 bits per second. The frame bits are themselves 12
Since the bits are grouped together in groups of bits (which form special broadcast channels), the actual transmission rate is typically 56 bits or more for each channel.

Preferably, data is sent in backup for each channel. The various 1W devices thereby identify themselves and send data including error checking bits and the like.

Each time slot containing 8 bits is numbered from the frame bits, channel 11 channel 2, and so on. The downstream data bits are modulated with a carrier frequency of, for example, 12 hiHz, and the upstream data bits are modulated with a carrier frequency of, for example, 6 M
Preferably, a 6 MHz carrier is modulated with the upstream data bits, for example a 6 MHz carrier.

Apparatus and methods for polling stations, transmitting data during various time slots, receiving data from those time slots, and transmitting data to a digital translation device such as a computer are well known. ,
A detailed explanation of this will be omitted.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to the drawings.

Reference is first made to FIG. 1, in which a block diagram of the apparatus of the present invention is shown. The device has a head end 1 connected to a transmission medium 2. Transmission medium 2 is Narube (coaxial cable is used, but optical fiber etc. may also be used. Branch transmission line 3
is connected to the transmission medium. To that end, this device resembles a conventional cable'ff distribution device.

However, instead of having a subscriber distribution divider connected to the branch transmission line, a subscriber distribution terminal 4 as described below is connected to the branch transmission line 3. A plurality of subscriber drops, for example twelve, are connected to the distribution terminal 4. At the subscriber's house, the subscriber terminal 6 is connected to the subscriber drop. Each subscriber terminal has a control signal generator 7 connected to a keypad 8. A standard television receiver is also connected to the subscriber drop 5.

At the head end 1 a cable TV or other video source 9 is connected to a VHF modem 10. modem 10
is connected to transmission medium 2. A distribution control terminal 11 is connected to the modem 100 input terminal. This terminal device 11 is also connected to a data storage/control device 12.

The video signal to be distributed is from the video source 9 to the vHF modem 1.
0 and is applied to the transmission medium 2 as an analog VHF signal. The video signal is sent through a branch transmission line 3 and given to each distribution terminal 4. This is the second
As shown in the figure. FIG. 2 shows, for example, broadcast television channels 2-6 and the FM band transmitted downstream between 50 and 108 MH2.

At the same time, distribution control terminal 11 provides an interrogation signal to poll each distribution terminal, requesting transmission of stored data representing a service request by a subscriber terminal. In response, the bowled distribution terminal sends a signal representing the requested information during its designated or control time slot. The signal is given to the data storage/controller 12 via the branch transmission line, the transmission medium, the VHF modem IO, and the distribution control terminal 11.

Preferably, the DB-1 packetized transmission format is used. Since the 1 and FM signals are sent to the subscriber terminal at 50 MHz or more, it is preferred to modulate the DB-1 data stream with a carrier wave and send it in two signals at frequencies between 11 and 14 MHz. For error checking (FIG. 2) one of the two signals is the inverse of the other. Upstream from the distribution terminal towards the head end.

The data signal traveling in the direction has a frequency of 4.5 to 11 MHz,
Must be within the numerical range.

As mentioned above, each dispensing terminal 4 includes an egg number converter controlled by a microphone processor.

One converter is provided for each subscriber drop 5.

If a service is requested by a subscriber in which more than one channel is provided at a time, one or more converters can be used for each subscriber drop.

By using a distribution terminal that re-formats the data and sends it to the head end, i.e. acting as a buffer, one of the major problems in such devices, namely the distributed subscriber terminals, is solved. The problem of picking up noise from the device is largely resolved.

A subscriber desiring to call a particular television service or channel enters a calling code and a channel selection code via the keypad 8. The control signal generator then generates the data signal. Distribution terminal 4
scans each subscriber drop in turn and, upon detection of a signal from the control signal generator, a microprocessor within the terminal stores a signal indicative of a service request. The microprocessor then compares the request to the lookup table and determines whether the requested service can be provided to the subscriber drop. Alternatively, the questionnaire can be stored within the subscriber terminal. If the type of service is extended at the subscriber, and if it is a requested converter service, data is sent to the distribution terminal and the converter sends the requested channel to the subscriber drop. make it work. At the subscriber drop, the channel is received by the TV receiver 13 in the subscriber's home.

The 'ff receiver 13 is tuned to channel 2 or 3, for example, and the output of the converter is applied to that channel. If two converters are used and two channels are selected, one TV receiver is tuned to channel 2, the other to channel 3, or ifllJ to any other free channel. I am made to do so. Data is also given to the head end.

to indicate that a particular channel has been selected. This can be used for billing or polling.

When visual data or other types of video services are requested, the microprocessor in the distribution terminal 4
VRAM that outputs to the VHF bus that provides data to the converter
Call local video controllers, including: Calls to VRAM M, of course, depend on whether the subscriber has power available to call this service.

If a certain data signal input from the keypad 8 requests the transmission of a data signal from the head end or the interrogation of a device at the head end, the requested information is stored in the distribution terminal 4. , that information is sent when the distribution terminal is bowled.

Next, the third section shows a block diagram of the distribution control terminal.
See diagram. Branch transmission m3 is video signal and bidirectional DB
-1chi1 data signal high-pass filter 16 separates the TV signal from the data signal;
These TV signals are given to the positive bus 17. The tube signal is applied to the input terminal of converter 18. In Figure 3, f
Two transducers with m transmission sections are shown for each transducer. An output terminal is connected to a corresponding diplexer 19. The output terminal of each diplexer is connected to a corresponding bidirectional subscriber drop 20.

The other input terminal of each diplexer is connected to a modem 21,22. The modems 21 and 22 are connected via a synchronization circuit 27 to a data input terminal and an output terminal of the microprocessor section, respectively.

The DS-1 data signal is applied to modem 26 through a low pass filter. A digital data signal is applied to the microprocessor 23 via a synchronization circuit 27. Similarly, a digital data signal is provided from the microprocessor 23 via the synchronization circuit 27 to the modem 26 and via the low pass filter section to the transmission line 3.

An interactive video module having multiple parts that can be called individually is also provided. The output terminals of those sections are connected to VHF bus 17. .

A control input terminal 1 is connected to the control bus, and a data input line 29 is connected to the microprocessor 23. Also connected to modem 26 is bidirectional data line 30 .

The signals from branch transmission line 3 must be split equally. One of the divided signals is applied to a high-pass filter 16, and the other is applied to a low-pass filter 25. Low pass filter 25 also includes a diplexer. This diplexer is DB
3-1 signal and sends it to modem 26. The diplexer inserts the generated DB-1 data signal into the distribution terminal and sends it to the head end via the transmission line feed.

The other part of the signal is passed through a high-pass filter 16 to VHF.
given to bus 17. This signal includes a video signal and an fm signal. Divide those signals into equal parts as much as possible. Each portion is for each converter (preferably two allocated for each subscriber drop).

The output of interactive video module 28 is also provided to the VHF bus. A video module with four video displays includes four rf modulators. Those modulators are V
RAM K is connected. This VRAM provides the wr bus signal. The signal is selected by the subscriber for the last song.

The modem 6 converts the DB-1 bit stream received from the head end and then sends it to the synchronization circuit 27 and the microprocessor 2.
3 and their auxiliary circuits. Modem 6 receives two DS-1s from the control unit.
The bit stream is also modulated and sent to the end of the head.

The modem 21 receives signals from 12 subscriber drops into one
The Dllll-1 bit stream is combined into two Dllll-1 bit streams and supplied to the control section. The modem 22 also transmits the generated bit stream to 12'
to the subscriber drop control unit. To protect personal confidentiality, output data to each subscriber is only released during the time slot assigned to that subscriber. modem 21
, 22 are controlled by a microprocessor 23 via a time slot selection bus (not shown).

The control section consists of a timing and synchronization circuit 27, a microprocessor 23 and associated memory. Commands from the head end are given to the control unit through the DB-1 channel, and information is sent to the head end when a command is received. The control unit controls and monitors the 12 subscriber terminals connected to it via subscriber drops, preferably using time slot 1, and controls and monitors the 12 subscriber terminals connected to it via the subscriber drop, and controls the IL distribution terminals, such as channel selection, assignment of interaction video module units, etc. Controls all internal functions of the device.

Microprocessor 23 scans each subscriber drop 20. In most cases it receives an idle message. Upon receiving a request for service via diplexer 19 and modem 21, microprocessor 23
examines its internal memory and determines that it can respond to the service request. If the service request is for the selection of a new channel, a signal from the microprocessor is sent via the car control bus to the associated converter, which causes the channel selection to be done digitally and sends the signal via diplexer 19 to subscriber drop 20. Let me send it.

As mentioned above, the DEI-1 format consists of frames each having 24 time slots. Each time slot forms an effective 56 bits/second channel. Therefore, all 12 subscriber stations simultaneously send 8-bit messages containing control information during the same timeslot (eg, timeslot 1). The control information may include TV channel change requests and numbers. The microprocessor operates each diplexer sequentially (or in any desired order) to separately scan the input 8-bit message.

When a non-idle message is received, the associated diplexer is preferably enabled at least twice as long to match the three messages received to check for errors. Preferably, the microbus cell will respond to a non-idle message by sending the same message back to the subscriber terminal as an acknowledgment. Therefore, the distribution terminal can distribute a total of 12 subscriber terminals in 30 ms (2.5 per subscriber terminal, S
It can be scanned in less than IJ seconds).

The data channel to the subscriber unit is divided into a low signal channel and an open signal channel. The A and BQ signal channels are the least significant bits of each time slot in each separate 12th frame.

Since one time slot is allocated for each subscriber station, each subscriber station has a total of 66 ae 7 )/s 0 capacity per subscriber station, and the 12th One cause bit can be sent per frame.

The A signal channel is used to send signals from the keyboard to the VRAM (described later). When the keyboard is turned on, the subscriber terminal sends a message via the control channel (time slot 1) to the distribution terminal to inform it of the request. If VRAM is available, the distribution terminal sends a message during time slot 1 to inform the subscriber terminal. The distribution terminal then sets its connection memory and sends all information to the VRAM via the A channel (also via data input line 29). If all VRAMs are in use, the distribution terminal will
"Unavailable" message is sent to the subscriber terminal.

When a connection is made between the keyboard at the subscriber terminal and the VRAM at the distribution terminal, data from the keyboard is sent directly to the VRAM in an asynchronous manner. Message is VR
Sent to AM. The message must consist of a start bit, 8 bits of data, and a stop bit. The 8 bits of data consist of 7 ASO bits (l character) and 1 address bit (designating the keyboard).

VRAM translates those characters and uses the appropriate 7. Execute the C machine and send the information to the subscriber's TV.
The information can be displayed on the receiver or sent to a database. This operation continues until the subscriber turns off the keyboard. When the keyboard is turned off, the subscriber terminal sends an 8-bit "off" message to the distribution terminal in time slot 1. The microprocessor then informs the VRAM and V
The connection memory is reset to stop sending information to the RAM, and the message is sent as a packet to the head end.

The B channel is not used for converter operation.

The data received from time slot 1 and the A signal bits of the bit stream coming from the subscriber terminal are processed by microprocessor 23.

Next, refer to FIG. This figure shows a block diagram of a basic head end device. A microbus 35 is connected to the control bus, data bus, and address bus. ROM 36 and RAM 37 are also connected to those buses. A special service device 38X/II control device, which will be explained later, is connected to a data bus 2, an address node, and a signal channel interface 39.The output terminal of this interface 39 is connected to a multiplexer 40.
, 41 and the main modem 42 to the output DS'-1 stream. Transmission medium 2 is connected to the output terminal of modem 42. The input terminals of the drivers 43 , 44 are connected to the transmission medium 2 via the modem 42 , and the output terminals of the drivers 43 , 44 are connected to the signal channel interface 39 . A clock and control circuit 45 is connected to interface 39 and multiplexers 40.41. VHF
A video input to modem 42 provides the VHF video signal for transmission over transmission medium 2. 'V'H
F modem 42 corresponds to modem 10 in FIG. 1, and the remaining elements correspond to distribution control terminal 11 and data storage/control device 12 in FIG.

The DB-IA signal channel is used to exchange message codes between the distribution terminal and the head end device of FIG. These message codes include codes required for control and special 'service requests, such as video channel requests, visual data requests, subscriber polling, etc.

Each message is U bits long and consists of an 8 bit field used for the code, a 13 bit field used for the address, and 3 bits for parity checking.

The address structure is preferably as follows.

That is, 3 bits are for intermediate repeater addresses (if any) (for up to 8 repeaters), 5 bits are for intermediate repeater addresses (for up to 8 repeaters),
5 bits for the subscriber terminal address for up to 32 subscriber terminals attached to each repeater-splitter, 5 bits for the subscriber terminal address for up to 12 subscriber terminals per distribution terminal It is. Each message is
Take all bits reserved for the A signal channel in each A signal frame.

The head end polls each distribution terminal in each second signal frame, and the other signal frame polls each distribution terminal in each second signal frame, and the other signal frames are used for the distribution terminal to send its own messages or to relay messages from the microcomputer. be reserved. The head end expects a response to each ball message and a confirmation message to each second message.

A signal channel interface device receives messages eight pits at a time in parallel from microcomputer 35 and inserts the messages one pit at a time into the output DB-1 bit stream. Meanwhile, it strips off the input message from the input bit stream and applies it to the microcomputer in parallel, eight bits at a time. Signal channel interface 39 must also include parity check circuitry.

Because the microcomputer 35 operates at a clock speed that is completely different from the DS-1's clock, it requires a clock and control circuit 45 that is completely independent of the microcomputer's clock. This circuit 45 supports the DS-1 signal format described above, i.e., 1.544 signals per second.
DS-M bits, that is, 8000 frames per second, each frame containing 193 bits.
1 signal format. Continuously sandwiched between each of the 6th frames < 8 of each time slot of the 12th frame
The th bit is used for signaling and for forming the A and B signal channels. Each channel is 24666
It is divided into bit/second data channels. Also, the frame bit inserted at the end of each frame is 1 for synchronization and for identifying the A and B signal frames.
It follows a pattern that repeats itself every two frames.

Once each distribution terminal is polled under the control of the microcomputer 35, the signal channel interface 39 converts the signal to the ps-i format based on the clock and control circuit 45 and converts it to the multiplexer 40 (g
If two inverted channels are used, the 11-14 MHz band (conversely to multiplexer 41) is applied to the input terminal of modem 42 for transmission to the distribution terminal. 8X 1.544M
H2). A response indicating that a request for a special 'ff service has been received via transmission medium 2 is converted to a lower frequency in modem 42 and transmitted to driver 43.
The signal is provided to the signal channel interface 39 via the signal. At that interface, the response is visible to the microcomputer 35 via the control bus, address bus, and data bus.

Special service equipment 38 sends equipment data messages containing control data, such as pay TV viewing hours, to central computer 46 and sends data messages from the central computer to microcomputer 35.

Reference is now made to FIG. 5, where a basic subscriber terminal is shown. The subscriber terminal includes a modem 50 connected to the subscriber terminal 20. A g-rate type N receiver 51 is connected to the modem 50.

Input data signals and output data signals are transmitted between timing and synchronization circuit 52 and modem 50. A microprocessor 53 is connected to the timing/synchronization circuit 52, and a bidirectional output terminal of the microprocessor 53 is connected to an asynchronous bus 54.
connected to. A keypad 55 and a keyboard 56 are connected to the asynchronous bus 54.

An asynchronous bus 54 is shown in FIG. At least one jack 57 is connected to this asynchronous bus. In practice, asynchronous bus 54 is preferably routed throughout the subscriber's premises. The two unused wires of the four-wire telephone cable can then be used for it.

An addressable 0ART 58 is plugged into jack 57. A keypad 55 is connected to a keyboard scanner 590 input terminal. The output terminal of the keyboard scanner is mouth A.
Connected to the input terminal of RT 5B.

The output terminal of 0ART 58 is connected to the input terminal of display driver 60. This display driver controls the operation of the numeric display 61.

Microprocessor 53 sequentially polls all devices connected to the asynchronous bus. The polling style consists of two messages. Each message consists of 11 bits: 1 start bit, 8 data bits, 1 parity bit, and 1 stop bit. As for the eight data bits, the first message consists of seven address bits and one mode bit to indicate that this is an address. Second
The message consists of seven data bits and one mode bit indicating that it is a data message. The data rate is 2.4 bits/second.

UART (universal asynchronous
us receiver-transmitte, r
) takes out the signal sent via the bus, and if the address matches the address set at the input terminal of 0ART, it receives the next message sent by the microprocessor 53 and receives the seven received data. Hold the bit.

Immediately after the microprocessor sends its polling message, the microprocessor switches to receive mode and waits for a human message. The message received is from the last device polled. This message consists of two edicts. The first word is the address of the sending device and the second message consists of B bits of data.

The microprocessor 53 activates the keypad 55 once per second.
Poll 0 times. This poll consists of the keypad address followed by seven data bits. Those 7
One data bit is the last selected television
It consists of two BOD coded bits that determine the number of channels. Those bits received are retained and provided as binary encoded data to a display driver 60 and from there to a numeric display 61. The lower four bits drive the l digit display, and the remaining three bits drive the lO digit display. Numbers 0 to 7 can be displayed using 3 bits, so 80 channels (0 to 7
9) can be selected and displayed.

Immediately after OA and RT receive the poll, 0ART sends a pair of messages. A scanner 59 continuously scans the keyboard 55 and holds the last numeric key pressed. The first message contains the address of the keypad and the second message is an 8-bit message containing information about the last key pressed.

Usually this is the same number as the previous pole. In this case, the microprocessor is not used. However, the new TV
When the button indicates that a channel is requested, the microprocessor sends information to the distribution terminal via the control channel 17 in time slot l. If this request is accepted by the distribution terminal, microprocessor 53 sends the new channel number to the keypad as described above and the distribution terminal changes the channel converter to the selected channel.

FIG. 5 shows a typical converter used in the distribution terminal 4.
, is a block diagram of an embodiment. A VHF bus 65 is connected via a wideband amplifier 66 to a low pass filter 670 input terminal. This filter passes all signals below 300 MHz. The output of filter 67 is applied to transformer 69 via hybrid 68. If desired, one of the terminals of the hybrid 68 can be connected to the second rank of the twelve powerhouses, but otherwise the terminal is terminated with, for example, 50 ohms.

The transformer 69 is connected to the emitter of a common base transistor 70 via a resistor 71. A video signal is provided from the collector of transistor 70 to mixer 72 .

The output terminal of local oscillator 73 is also connected to mixer 72. Local oscillator 73 is preferably configured as a digitally controlled phase-locked loop. A digital selection input terminal of local oscillator 73 is connected to the microprocessor via data bus 74. The microprocessor is the microprocessor 23 of FIG. 3, and the data bus 74 is the control bus of FIG.

Thus, when a channel selection request is received by a data word applied to the digitally controlled phase-locked loop comprising local oscillator 73, the local oscillator signal is mixed with the input video signal to produce an intermediate frequency signal.

The intermediate frequency signal is applied to a very sharp bandpass filter 77 via a filter 75 and an amplifier 76. filter 75
can be composed of a two-pole LO filter, and the center frequency of the bandpass filter 77 is an intermediate frequency. This bandpass filter is assumed to be a SAW filter.

In one embodiment, the local source N is 430 to 680
A digitally synthesized signal of frequency MH2 is generated to yield an intermediate frequency of 380 MHz when mixed with the input signal.

The output of filter 77 is applied to one input terminal of mixer 78.

An oscillating signal of another local oscillator (not shown) is applied to all converters t\ used in a particular distribution terminal. This signal is applied via a resistor 80 to the emitter of the grounded base l.

This signal is applied to tank circuit 81 to maximize the amplitude of the signal. Part of that signal is noibrid82
0 input terminal. The signal appearing at the output terminal of hybrid 82 is applied to a second input terminal of mixer 78. As a result, the intermediate station signal converted to a lower frequency is provided to the band elimination filter 83. the result,
The intermediate frequency signal passes through the lower pass portion of filter 83.

Alternatively, an LO filter can be used instead of a SAW filter. A SAW filter is inserted in the signal path between mixer 78 and filter 83.

The fm signal is applied to the emitter of another common base transistor by a resistor 85. The compensation resistor from resistor 85 is f
m signals can be passed on to the next transducer.

” The collector of the transistor 84 is the band-stop filter 8.
3 high-frequency partial pressures are connected.

For example, if the local oscillator signal applied to transistor 79 is 436 MB2, the signal is 380 MB2.
By mixing with the intermediate frequency signal of the ribs, the output signal of mixer 78 becomes TV channel 2. fm 88-108
This signal, which is in the MJiz band, is applied to a subscriber drop 87 via a band division filter 86. Model A 21
, 22 is connected to a band splitting filter 86. Therefore, the filter 86
A diplexer 19 shown in the figure is formed.

When the second channel is selected, the second converter is used and outputs to the channel J14 which is different from the first channel.

FIG. 8 is a block diagram illustrating the interactive video module 28 shown in FIG. 3 in more detail. This figure shows a block diagram of units in a distribution terminal that is shared among a plurality of subscriber terminals.

In general, this allows up to 1632 characters to be displayed on the screen of a pf TV receiver without any modification, and with appropriate configuration, up to 25 characters can be displayed on the screen of the receiver.
Color graphics display of 6 x 256 points can be performed.

The structure consists of a data link controller, a microprocessor, memory, and a video display generator.

The DB-1 stream from modem 1 (FIG. 3) is connected to data link controller 96 via cable 95.

This controller 96 is connected to the modem 2 via an output buffer 97.
6 (FIG. 3). Data link controller 96 is connected via bus 98 to microprocessor 99 which in turn is connected via bus lOo to microprocessor 23 (FIG. 3) and via lead 29 to the A channel bit source. Be connected to.

Microprocessor 99 is connected to multiplexer 102 via bidirectional address and data bus 101. The memory 103 is connected to the output terminal of this multiplexer o2.
are connected to these multiplexers 102 and memory 1
03 is connected to the video display light platform o+. The output terminal of this video display generator is connected via modulator 105 to VHF bus 17 (FIG. 3).

Generally, memory 103 stores characters provided from a visual database at the head end or from a subscriber terminal. Video display generator 104 generates the composite video signal necessary for displaying information on the screen. A modulator 105 then modulates this composite video signal to the desired TV channel and sends it to the correct address.

Assuming then that the subscriber is allowed to call the converter in the distribution terminal as determined by a lookup table stored in the main distribution terminal microprocessor,
The unused TV channels can be called upon request by their converters.

When the subscriber enters data on the keyboard 56 (FIG. 5), the data is displayed on the underside of the TV receiver. being requested (the request is being displayed on the screen)
When the subscriber wishes to retrieve the data, the subscriber presses the return button. Then, the microprocessor 9
9 converts the message into an HDI;O formatted message and sends the information as high speed data packets to the head end and then to the video text database.

Keyboard 56 is invoked as previously described with respect to keypad 55 (FIG. 5). When scanned from the distribution terminal, data is provided via a manual buffer 95 to a data link controller 96.
sends information to display memory 103.

A video display generator 104 converts the data information into the composite video described above and sends it to the VHF HAS via a modulator 105. The composite video is brought up on the subscriber's TV screen as described above with respect to the broadcast 'ff channel. However, when the return button is pressed, the data link controller sends the information in the display memory to the head end in the selected time slot. The data link controller consists of a multiprotocol chip, such as the Model 6854 controller available from Motorola, Inc., and an input buffer 95 and an output buffer 97. The data link controller is controlled by a 4 microprocessor 99 using timing signals from the distribution terminal timing and synchronization circuits.

Signals are sent in two paths. In the direction from the head end distribution control terminal to the distribution terminal.

The data link controller 96 constantly sends information directed to the circuit in which it resides. To perform this function, (,zl) the human buffer 95 stores 1.
544MH2 in 8-bit time slot l. The human cover 95 then clocks 56 bits/second into the input io of the data link controller 96 in the most significant bit of this time slot.

(b) Data link controller 96 always looks for the HDLO flag character. If the flag is detected, the microprocessor 99 is informed accordingly.

The data link controller 96 then sends the received eight bits (address bits) to the microprocessor 23 of the distribution terminal 4. If the bits match the local VRAM address, the microprocessor informs the data link controller 96 and enters receive mode.

(C) The next 8 bits received are control bits.

These eight bits are sent to microprocessor 99 to check their validity. If those bits are not valid, the microprocessor will use HD! ,
Forms the signal sent to the head end via the O signal protocol.

(d) In the reception mode, the data link controller 9
6 sends the characters it receives directly to microprocessor 99, eight bits at a time. Then, the microprocessor 99 memorizes this data! Send it to the correct storage location in J103.

(θ) The above operation continues until the data link controller 96 detects the second flag. Detection of the second flag by data link controller 96 indicates the end of the message. The 16 bits before the flag are error checking bits.

'The data link controller examines these error check bits to determine whether a valid message has been received. If a valid "Itx" message is received, the data link controller informs the microprocessor 99 and returns to the idle link state (to look for the flag). Notify the department.

If the error check is incorrect, then the transmission was in error. Then, the microprocessor 99
A message such as (transmission) + 珀线transmission error 盙蒼 is displayed on the screen of the TV receiver, this is notified to the database, and the transmission of the signal is waited. If the transmission is received, a new character will be displayed to confirm the transmission. At this time, on the bottom line of the screen, the character ``Gang Roryo'' whose transmission has been corrected will be displayed.

For transmission from VRAM to DC3T 11, all VRAMs in the entire device are placed in time slot 1 on a contention basis.
call. This competition base is based on one VRA.
When M is calling a channel, no other VRAM can transmit until that VRAM has finished transmitting. The VRAM determines whether the channel is in use by checking whether the received transmission is in a valid idle link state. Since idle link messages are sent whenever an upstream channel is available, it is possible to determine upstream status by examining the downstream channel.

The actual transmission is controlled by microprocessor 99. It is constantly updated by the receiving part of the data link controller 96 as to whether the device is in an idle link state. To be in a valid idle link state, the receive path must remain in an idle link state for a given number of similar frames. The number of frames between the idle link state and the valid idle link state is any number between 0 and 4 and is selected by the microprocessor. The purpose of this delay is to prevent several VRAMs from attempting to transmit at once after a long DOT-VRAM transmission.

If the microprocessor 99 determines that the subscriber wishes to send from his keyboard, the microprocessor sends an 8-bit address character (VRAM address) to the data link controller 96. The controller then generates an 8-bit flag frame,
Send address character. Controller 96 effects the transmission of its address characters by generating a 56 bit/second data stream on its output pins. Its output is fed to a buffer 97 which adds one bit after every seventh bit (to form a data stream of 7 seconds of data at 64). 8 bits of data is 1.544 between 10 time slots
MHz clocked (8000 times per second).

The microprocessor then follows the address characters (8 bits) with the control characters, followed by the alphanumeric characters (ASO 17 bits and inverted display bits). The alphanumeric characters are also those that the microprocessor wishes to send. The microprocessor then terminates the transmission by notifying data link controller 96 that the character sent is the last character. Then, jilJ
Controller 96 generates and sends a 16-pit error check message and an 8-pit error check message, and then returns to the idle link state.

Microprocessor 99 receives all signals and data received by the various input terminals to the VRAM and
It controls the operation of the AM and informs the microprocessor of its status. Microprocessor 99 connects data link controller 96 and bus 100 to microprocessor 23.
, channel bit information from microprocessor 23 , and address and data bus 101 to multiplexer 102 .

Data link controller 96 sends status information and 8-bit data words to microprocessor 99. A microprocessor uses state information to determine when it can send information and when it should receive information. Microprocessor 99 receives data words from the data link controller and uses those data words to determine whether the input data is valid and whether the data word is directed to this VRAM. If the data is destined for VRAM, the microprocessor retrieves the characters and sends them to the correct location in the appropriate memory 103.

(Some data are control words directed to the VRAM microprocessor. The microprocessor then performs the appropriate operations on those control words. When the message is finished, the microprocessor generates a code word and , forms a confirmation packet for the database. Data link controller 96 then sends this packet to the database at the head end.

Microprocessor 99 receives up to 4A channels of signal bits per frame. Due to previous communication with the distribution terminal microprocessor 23, it is informed which subscriber corresponds to which bit.

The microprocessor sends the bits to four registers (one register for each VRAM) and parses the information in those registers.

The transfer of information from the subscriber terminal via the A signal channel consists of one start bit, nine data bits,
Done in an asynchronous manner with one stop bit. Therefore, the microprocessor always initially looks for a start bit, and once the start bit is found, it uses the next bit to determine whether the input is from the keypad 55, keyboard 56, etc., and then Then, the next 8 bits are considered data bits. When 8 data bits have already been received, the microprocessor parses the 8-bit word and (a) displays the data;
Perform one of three operations: 1)) execution of a control operation, or (C) transfer of data.

To display data, the microprocessor first sets the color of the character and then sends the data to the correct memory location. The color of the character can be determined in advance by pressing the "color setting" key. In one embodiment of the invention, the color is selected to be green or orange, and the color indicating an abnormality is green.

The correct memory location is the video display generator 104.
is the memory address at which the character will be displayed on the bottom character line (dialogue window) of the TV screen when accessed by . The first character is placed in a memory location and appears on the left edge of the TV screen. Subsequent characters (up to 31) are placed next to the previous character. If more than 32 characters are entered, the correct character position is rolled and T
Start again on the left side of the V-screen.

If the received 8-bit data word is a control character, the microprocessor looks for that character in the table and then executes the appropriate subroutine to perform the desired function.

Typical functions of control characters are:

(1) Backward character: The last character in the dialog window is deleted.

(11) Deletion Character All characters in one dialogue are deleted.

(II+) Escape Character - This character tells the microprocessor that the next character received is control information rather than data. For example, a subscriber may wish to change parameters such as the background color. The subscriber does this by pressing the escape character button followed by the character button indicating the next color being requested.

Different numbers of colors for grids of different sizes, DATA PACK nodes using dedicated channels, or transmitting data to different network locations, calling timeslots other than timeslot 1, using a light pen. It is clear that various controls can be performed, such as interaction control, operating wand or keyboard cursor, software downloading. The program is available in the database,
Downloaded in VRAM memory for execution.

Upon receiving the return character, microprocessor 99 generates the address and control messages necessary to send the information packet and sends the information to data link controller 96. The microprocessor then sends the characters in the dialog window to the database by taking eight bits of data for each character from the corresponding memory location and providing it to the data link controller. When the last character is sent, the microprocessor signals it to the data link controller so that it can generate error detection bits and flower bits. The microprocessor also inverts all displayed characters to notify the subscriber that a message has been sent.

To preserve the ABCj style, the 7th bit used in memory to select the color is replaced with the correct bit of the ASO character.

The microprocessor then waits for a confirmation signal from the head end database and terminates its operation upon receiving the confirmation signal. If confirmation is received within two seconds or if an incorrect sequence number is received, the microprocessor will resend the message. Retransmission of the message will be attempted up to three times.

If all three attempts fail, the microprocessor displays 8" Transmission Failure on the top line of the dialogue window and inverts all characters again.

If desired, the subscriber can then retransmit the character by pressing the return key.

A third signal source received by the microprocessor is
A control signal source generated by microprocessor 23. The signals are received in asynchronous mode via serial lines using the asynchronous ports of each microprocessor. The line is used to send information from the distribution terminal controller to the VRAM about the service requested by the subscriber, the subscriber's address, and the time slot used by the subscriber. When the subscriber turns off the keyboard, the information is sent to the VRAM microprocessor 99.
It will be done.

In the reverse direction, the VRAM signals the microprocessor 99 that it can use the video display generator, and once the connection is completed, the VRAM
The RAM sends the total number of confirmation packets that the subscriber has generated since the subscriber connected.

The final set of signals communicated to and from the VRA,M microprocessor 99 are found on the memory bus 101.

The memory bus consists of a 12-bit address bus and an 8-bit bidirectional data bus. This bus is used by the microprocessor to place information received from data link controller 96 into the correct location in VRAM memory 103 in order to appear in the correct location on the TV screen. “The memory node is also used to retrieve information stored in memory and displayed on the TV screen and send that information in packets to a database at the end of the head.

VRAM has a completely independent memory block of 512 (increasable) 8-bit bytes.

These memory blocks are accessed by VRAM microprocessor 99 and video display generator 104.

The VRAM microprocessor accesses all memory blocks in parallel via memory bus 101. It is preferred to have four video display generators for twelve subscribers, but the number used depends on the amount of traffic experienced. Each video display generator accesses one memory block independently of the others. The video display generator normally addresses and reads the contents of the memory block. However, a multiplex gate 102 is included so that the microprocessor disables the video display generator whenever memory is attempted to be recalled.

Each video display generator is a large scale integrated circuit that reads data from memory and generates a composite video signal that allows alphanumeric or graphic displays to be generated. Those circuits were manufactured by General Instruments (Ge) in the United States.
neral Instrument). The composite video is output by modulator 105 to
Even unused television channels are modulated. Then, as described above, the VHF distribution bus]7
sent to.

[Brief explanation of the drawing]

1 is a block diagram of the apparatus of the present invention; FIG. 2 is a frequency diagram suitable for use in the present invention; FIG. 3 is a block diagram of a subscriber distribution terminal; and FIG. 4 is a block diagram of a head end device. 5 is a block diagram of a subscriber terminal; FIG. 6 is a detailed block diagram of a part of the subscriber terminal; FIG. 7 is a terminal of an interactive video module in a subscriber distribution terminal; FIG. 8 is a detailed block diagram of a converter used in a subscriber distribution terminal. 3... Branch transmission line, 4... Subscriber distribution terminal, 5゜20... Subscriber drop, 6... Subscriber terminal, 7
...Control signal generator, 11...Distribution control terminal device, 1
2...Data storage controller, 16...High-pass filter,
23, 35, 53, 99... Macro processor, 25... Low pass filter, 27... Synchronous circuit,
Country: Interaction video module. Applicant's agent Kiyoshi Inomata

Claims (1)

[Scope of Claims] (1) A central station, a plurality of subscriber distribution terminals, and a tree-shaped transmission device connecting the central station to each of the distribution terminals, each distribution terminal comprising: 1 for each of multiple subscriber terminals
each central office, each distribution terminal, and each subscriber terminal includes equipment for transmitting and receiving digital signals; data from each subscriber terminal can be conveyed to the central office by means of a television signal source located in a plurality of separate channels, and for each subscriber terminal, the terminal each subscriber terminal is manually operable to designate one television channel claimed as a television terminal; and an apparatus for generating a digital channel request signal in dependence on the requested channel, wherein each subscriber distribution terminal is configured to transmit a television channel to a respective terminal. a plurality of television converters each connected to a subscriber drop, and repeatedly transmitting a digital signal requesting said digital channel request signal to each subscriber terminal, said list of channels accessible by said terminal; a microprocessor device configured to receive from said central station a table thereof, and to compare said request signal with said table for each terminal; A two-way cable television control and transmission apparatus comprising: an apparatus for controlling each converter to provide a channel; (2. The device according to claim 1,
(3) The device according to claim 1, characterized in that each distribution terminal is configured to send data relating to channel request signals from the subscriber terminals to the central office. A device,
The converter control device includes a variable oscillator having an input device for controlling its oscillation frequency, and the microprocessor device receives information as the last channel request signal received from the subscriber terminal. and is configured to compare the received signal with a stored signal and to send a command to the input device only when a change between the received signal and the stored signal is detected. Featured device. (4) The device according to claim 2,
a device in the subscriber distribution terminal for storing a usage signal indicating which television channel each converter provides to the corresponding subscriber unit; and a device adapted to ball the subscriber distribution terminal. The apparatus further comprises a central control unit and a device at the terminal for providing a signal corresponding to the usage signal onto a transmission medium for transmission to the central control unit. (5) The device according to claim 1,
The subscriber distribution terminal includes equipment for scanning each subscriber drop, and each subscriber terminal includes a radem and a modem for applying the television request signal in digital form to the subscriber drop. a device for connecting a television terminal to a subscriber drop for receiving a selected channel; a keyboard data signal generating terminal; and connecting the keyboard data signal generating terminal to a control signal generating device. - a data bus. (6) The device according to claim 5,
a control signal generator generates the television service request signal as a binary coded signal in a predetermined channel of a time division multiplexed signal carried by subscriber drops having television signals at different frequencies;
A device characterized in that it is adapted to give and. (7) The device according to claim 1,
The distribution terminal comprises a bus for receiving a television signal including a plurality of television channels, the input terminal of each converter is connected to the bus, and each converter has a frequency determined by a control signal. a variable frequency local oscillator for generating the signal; a mixer for receiving the television signal and the signal from the local oscillator and outputting an intermediate frequency signal; and a second mixer for receiving the intermediate frequency signal and the second local oscillator signal. and further comprising a second local oscillator connected to a second mixer of the plurality of converters and outputting a predetermined fixed frequency signal. (8) The device according to claim 7,
further comprising a second plurality of transducers similar to the first plurality of transducers, the input and output terminals of the transducers of each building 2 being connected in parallel to one transducer of the first plurality of transducers; and further comprising a third local oscillator connected to a second mixer in a second plurality of said converters and outputting a second predetermined frequency. (9) The device according to claim 7,
Each variable frequency local oscillator consists of a digitally controlled phase-locked loop, with a microprocessor capable of controlling the frequency of each variable frequency local oscillator by applying a data signal to each said phase-locked loop, and a microprocessor that controls each subscriber drop. a modem device connected to the subscriber drop for translating the digital signals received from each said drop and providing those signals to the microprocessor, so that the phase corresponding to the subscriber drop to which the associated converter is connected; A device characterized in that a data signal is applied to the lock loop.