CDS Coding system by sync pulse removal
285 nominal dollars (CDS-C)
24 nominal dollars (CDS-D)
Fig.1 - Encoder CDS-C (1 - video input,
CDS coding system (Coding by sync pulse removal) is intended for arrangement of commercial TV broadcasting. It enables to control access of each TV network subscriber to TV channel or program viewing broadcast in the CDS system. The CDS system can service up to 64 TV channels with the quantity of 32000 subscribers. The CDS system can be used in all the frequency ranges of over-the-air and cable TV broadcasting. Hereafter the encoder is designated as CDS-C and the decoder is designated as CDS-D.
The CDS-C Encoder is intended for video signal encoding according to the CDS system standard. The coding lies in video signal component coding. Namely in:
* sync pulse marking by luminance signal
* introducing of control signals by CDS system decoders
Besides the encoder has additional functions which improve output video signal quality:
* AGC of luminance signal swing;
* noise burst limitations in an amplitude area of composite sync pulse;
The encoder can be used as a part of equipment of the TV studios broadcasting in the PAL chromaticity system.
Each encoder in the CDS system has its functional number - the identifier. This number is indicated on the label of a device. The functional number of the encoder may be within 0 and 64.
The principle of the encoder operation lies in the amplitude behaviour change of video signal elements and in injecting of additional signals which provide encoder operation of the CDS system.
The encoded signal can be visible on a TV set screen accompanied by a skip when a bright freeze-frame appears.
The Subscriber CDS-D Decoder is intended for signal decoding of commercial TV channel broadcasting operating in the CDS system.
Fig. 2 - CDS-D Decoder
1 - "F" "RF IN" socket to connect antenna cable to the decoder input;
2 - "F" "RF OUT" socket to connect the decoder output to the TV set antenna input;
3 - plug to connect video signal from TV set; 4 - power supply
Starting-Up and Adjustment
Connection of CDS-C Encoders Connection of the encoders should be done according to fig. 3.
Fig. 3 - Encoder Connection Scheme
Attention! A connection cable to a computer is unique. It can not be exchanged with an RS-232 standard cable. There is an RS-232 communication protocol converter into a RS-485 communication protocol in one of the cable connectors. A cushion should be set into a free communication protocol connector of the remotest encoder from the computer.
The application NetClient is intended for subscriber decoder status change. The decoder status for each received channel can have two meanings: "decoding allowed" and "decoding forbidden". The NetClient application operates on the computer which is compatible with IBM with WINDOWS 98 SE, ME, WIN 2000, WIN XP OS. To install the application a CD with a distribution disk should be put into a turntable drive and the instructions of the installation-program should be followed. An offline COM port of the computer (COM1 or COM2) should be chosen on the "Clients" bookmark for application operation. If the chosen port is free and is being opened a green indicator flashes on. Otherwise a system message is generated. If a data cable is connected to the computer a red indicator flashes on.
After the first start a database file MyBase.ch is created in a current catalog which stores information about the subscriber decoder status.
The database creation should be begun from the "Devices" bookmark, where the list of the connected encoders is made by flagging in those lines which have the IDs equal to the connected encoder identifiers..
The channel can be renamed if necessary by marking the line with the needed channel and pushing the "Rename" button.
When the "Scan" button pressed the application scans the communication protocol and places the found encoders into the "State" column.
Push the "Check All" button to mark all the found encoders. Push the "Uncheck All" button to cancel the marking.
Push the "Clear" button to clean the database of the marked channel if necessary.
Afterwards the subscriber decoder number (in the box "Client number" from the "Clients" bookmark) which is to be entered in the database should be typed.
Each decoder has its unique number which is a number for the database. An existence flag of the decoder should be set in the "Exist" box afterwards. It enables speeding up access to the subscriber decoder (absent decoders will be ignored).
Afterwards those channels should be flagged in the channel list viewing of which is allowed to the subscriber (decoding allowed). The personal data of a subscriber can be entered into the corresponding lines.
The number of the next subscriber decoder should be typed afterwards till all the subscribers are entered into the system. Afterwards the information about the subscribers should be transferred to the encoders by pushing the "Update" button. The progress of the command fulfilment can be watched in the "Log" box.
It is recommended that the "Update" button should be used after the initial database creation. If the changes or additions will be made it is recommended that the "Smart Update" button should be used. In this case not the entire database will be transferred to the encoders but only its changed part.
Push the "Verify" button to compare the content of the computer database to the encoder database.
In the "Devices" bookmark one of the algorithm of subscriber governing ALG_1 or ALG_2 should be chosen. If the algorithm ALG-2 is chosen the control order is sent only those subscribers who have the "Exist" flag in their database (registered subscribers). It enables shortening the time to fulfil the commands of subscriber status change. It is a basic algorithm.
If the algorithm ALG_1 is chosen the control order is sent all the subscribers successively from the 1st to the 32000th number. If unconsidered decoders appear in the cable network they will receive a command "decoding forbidden".
When the flag "Encrypt" is set on the "Devices" bookmark encoded signal with service information will be transmitted from the "Video out" output of the encoder When the flag "Encrypt" is unset on the "Video out" output of the encoder uncoded video signal with service information will be transmitted.
The application NetClient can be closed afterwards till the next change of the database.
The subscriber status information is stored in the permanent memory of the encoders.
CDS-C Coding System Update
The CDS coding system has a function of the software updating for the CDS-C encoders. The following operations should be carried out to do it:
1. A +12V power of the CDS-C encoders should be switched-off.
2. All the power jumper cables (they are turned on between the power connectors of the encoders) should be taken off.
3. All the jumper cables of the communication protocol should be removed.
4. A communication protocol cable should be connected from the computer to one on the encoders.
5. A +12V power cable should be connected only to this encoder. Do not energize the encoder!
6. Launch the NetClient application on the computer.
7. Chose the necessary COM port number on the "Clients" bookmark.
8. Chose the "Devices" bookmark, chose the "Hex File" button at the bottom with a mouse click and chose the "mainX.hex" file where X is the number of the encoder being programmed currently.
9. Push the "EEP File" button in the same way as described above and choose the "main.eep" file. This file is the same for all the encoders.
10. Push the "UpLoad" button. The message "Waiting Signal From Device" should be displayed. This mode can be cancelled if necessary by pushing the "Stop" button on the "Clients" bookmark.
11. Afterwards the encoder being programmed can be energized with a 12V power. The programming begins automatically. It is possible to watch the progress of the process execution in the "Log" box. Turn off the energizing of the encoder after the programming.
12. Connect the communication protocol cable connector to the next encoder, chose a new "mainX.hex" file which corresponds to the connected encoder number. The "main.eep" file should not be chosen again.
13. Pass on to the item No.8. Perform the items 8-13 to reprogram all the encoders.
14. Renew all the power and communication protocol jumper cables.
CDS Setting up Procedure
The 1st item should be performed at the head-end.
1. Connect the encoders and the head-end modulators as shown in fig. 3 and inject 65-75 dB/µV signal from the head-end output to the "RF in" input of the CDS-D encoder (see fig. 2)(supposed that the encoder serial number is 1). Connect the "RF out" radio frequency output of the encoder to the rf input of a TV set. Connect the " VIDEO OUT" input of the encoder to the "VIDEO" output of the TV set. Energize the CDS-D decoder. Set an access to a subscriber decoder with a serial number "1" in the database of the NetClient application. Set on the TV set the number of one of the coded signals, for example it is the channel No.21. Pursue a stable image of the decoded 21st channel on the TV set screen with the help of the video signal level control on the modulator of the 21st channel of the head-end (see P.S.). Chose the next coded channel (for example it is the 23d channel) on the TV transmitter and pursue a stable image with the help of the video signal level control on the modulator of the 23d channel of the head-end. The operation is done in the same way at the same decoder with a serial number "1" (see P.S.). Tune the rest of the head-end modulators to which the coded video signals arrive in the same way. After the head-end modulators have been tuned (the modulators to which the coded video signals arrive from CDS-C) effect a control check by two or three decoders with other serial numbers.
P.S. The company recommends to control the video signal level at the head-end modulators with the help of an oscillograph, for example C1-64. The oscillograph should be connected to the video output of the TV set. As far as a decoder is connected to the video output of the TV set a three-way socket (RCA connectors)(the three-way socket is not a part of the set) should be used. Pursue that the oscillogram of the video signal at the video output of the TV set looks like in the fig. 4в with the help of the video signal control at the modulator. The difference between the blanking level and the black level should not be higher than 7%.
а) б) в)
1 - black level
2 - blanking level
а) the blanking pulse level is lower that the black pulse level;
б) the blanking pulse level is higher than the black pulse level;
в) the blanking pulse level coincides with the black pulse level.
Fig. 4 - Regenerated signal oscillograms
The Decoder Installation at Subscriber's Place
2 Before starting to install a decoder at subscriber's place the TV receiver of the latter (if it has no fixed channel selection but automatic tuning to channel) should be tuned to the channel which you are going to close because in the autosearching mode this "closed" coded channel will be not identified by the TV receiver because of a specific joint work of the coding device and automatic frequency control of a TV set. A blue field appears on screens of some TV receivers when input rf signal is absent. As a rule there is a possibility to avoid this mode from the TV receiver control board. Turn off the "blue field" to provide a reliable operation of the decoder.
Remember, that the input rf signal arriving to a decoder should be of a 65-75dB/µV level to provide the operation without overloading.