BLAUPUNKT MS 63-76 B Chassis FM100-30 DTS Units VIEWING.

- Stereo Sound Decoder Unit (Stereo-Decoder-Modul) 866830617 with TDA6600 + TDA6200 (SIEMENS)

- Luminace + Chrominance Unit (signal modul) 8668304970 (Note the hybric IC it seems a
Motorola TDA3301 but not sure)

- Tuner Unit 8 668 812 770

- Teletext Unit (VideoText modul) 86530F1 with PHILIPS SAA5231 + SAA5240P/B + Toshiba TC5565P-15 (RAM PAGE)

 

This invention relates to teletext decoders for receiving, storing and processing teletext information which is transmitted as digitally coded data and comprises a plurality of different pages each of which is identified by a respective page number. Transmissions of teletext information are in television signals in television lines where no picture signals representing normal television picture information are present. These television lines are referred to as data-lines. 

 

The document "Broadcast Teletext Specification", September 1976, published jointly by the British Broadcasting Corporation, Independent Broadcasting Authority and British Radio Equipment Manufacturers' Association, discloses a specification for transmitting teletext information in 625-line television systems.

In the above-identified document "Broadcast Teletext Specification", a quantity of teletext information to be considered as an entity is termed a page and will be so termed herein. All of the pages which are available are normally transmitted in a recurrent cycle, with or without up-dating page information, as appropriate. At a teletext decoder any page can be selected, and the digitally coded data representing the page information is then acquired by the teletext decoder from the cyclic transmission and is stored in a page memory of the teletext decoder for as long as the page is required. A teletext decoder may have a multi-page memory having a plurality of memory portions in which individual pages can be stored. These memory portions may be used on a priority basis, that is, if two (or more) memory portions are allotted to store the same selected page, then priority logic in the decoder allows only one portion to receive the page in preference to the other(s).

The pages are organised into different magazines (or groups) and each page consists of up to 24 data rows. The first data row (Row 0) of each page is termed a page-header and contains inter alia the page number. The transmission of each page begins with, and includes, its page-header and ends with, and excludes, the next page-header which is transmitted in respect of a page in the same magazine. Thus, it is assumed that all of the data rows containing the relevant magazine number which are transmitted between two such successively transmitted different page-headers belong to the page having the first page-header.

Proposals for enhancing the teletext specification given in the "Broadcast Teletext Specification" document are given in the document "World System Teletext Technical Specification", March 1985, compiled by the Department of Trade and Industry. One of these enhancement proposals concerns the provision of a conditional access teletext service in which teletext message information in data pages is scrambled prior to transmission, and can only be received as useful information by a teletext decoder having an appropriate descrambling key. Such a descrambling key is itself transmitted as encrypted teletext information in the data page concerned, whilst other keys which are provided to regulate the conditional access to transmitted teletext message information are transmitted in encrypted control pages. Decryption therefore has also to be performed within the teletext decoder.

The SAA 5240 is a second-generation LSI teletext decoder. It takes over several of the functions provided by individual integrated circuits in the first-generation decoders, namely the SAA5040 TAC (this retrieves the teletext data from the video data-stream) and the SAA5050 TROM character generator that everybody who's ever used a BBC micro will be familiar with.
All of these functions are provided by the SAA 5240 Euro CCT, which greatly reduces the component count and makes for more reliable and compact hardware. In addition, the dot-mapping for the generated characters is on a 12x10 matrix instead of the original 5x9. However as the Ground Control receiver does not make any use of this facility, we won't discuss it further.

The video data-stream is split (by the VIP2) into data and clock, which is input into the Euro CCT. The data acquisition function searches for the requested page using an extremely flexible system (you can tell it to look for... from ANY page, to any page in a given magazine such as p1xx, right down to a specific sub-frame only, like p110.7).
The Euro CCT provides four parallel systems to search for pages, but this is not utilised by the Ground Control hardware - though provision has been made for it as a modification.
Once the page has been fetched, it is stored in memory. This facility is provided either for display by the Euro CCT itself, or for later transmission to a controlling computer via the IIC bus. It is perhaps  that the Euro CCT has a number of additional features. The first of these is that the Euro CCT includes a full character set generator and masking options. These might have been used to 'overlay' teletext frames on the output video signal, much as the same is possible with any TV set. The Euro CCT takes care of the re-sychronisation.

The VIP (SAA 5231 VIP)Video Input Processor is responsible for assessing the 'quality' of the input video signal, and (if the signal is good) for extracting the teletext data-stream and clocking, which is then presented to the Euro CCT.
A possible 'notable' function of the VIP2 which is not implemented in the Ground Control receiver is the 'VCR' input. This modifies the VIP2's internals slightly to allow better data extraction from a source which may contain jitter, such as a video recorder. With this, and suitable software, it is theoretically possible to extract "Closed Captioned" data from appropriately captioned videos.
The VIP2 does not connect to the IIC bus.

 Other References:
D'Amato, "A Software-Oriented Dual Standard Teletext Decoder", Rev. HF (Belgium), vol. 11, #11 pp. 373-380, 1981.
British Broadcasting Corporation et al., Broadcast Teletext Specification (Sept., 1986).
U.K. Department of Trade and Industry, World System Teletext Technical Specification (March, 1985).
Specifications for the Philips MAB84XX chip.
Specifications for the Mullard SAA5230 chip.
Specifications for the Mullard SAA5240 chip.