This invention relates to improvements in satellite transmission and receiving equipment.

Satellite transmission systems are enjoying high levels of market growth and increasing public awareness and acceptance. As the systems have grown in popularity the demands placed on the available technology has increased, as has the public's expectations of performance and ease of use. As a result it has become apparent that improvements would be desirable in relation to various aspects of the systems.

The quality of modern video and audio equipment is such that very high levels of picture clarity can be obtained from conventional television transmissions and from video tapes. However, as a result of the way in which satellite operates if there is a weak signal caused, for example, by the receiving dish being of insufficient size, by weather conditions, by mis-alignment of equipment, or whatever, significant noise can be introduced into the picture. This shows up on the receiving screen as black or white dots or

dashes which may result in a significant reduction in picture quality.

It is an object of the present invention to provide means of overcoming this particular difficulty.

Satellite systems generally work on the basis of having a decoder module which decodes the satellite signal received in order that the transmission may be accurately produced on screen. Such decoder modules may work in conjunction with a card system. This comprises of a card reader which allows the decoder to operate on insertion of an encoded card. Such systems are adequate when only one card is necessary to view the satellite channels available. However, there are instances where two or more cards may be required, each card providing access to a different set of satellite channels. The problem with such a system is that the cards may be easily misplaced and, in addition, the constant insertion and removal of cards into the decoder can lead to system malfunctions as both the card and the reader can wear with use.

It is therefore a further object of the present invention to provide a means of overcoming this particular difficulty.

A still further problem which has arisen with the growth in availability of satellite channels is that the-increasing number of channels available to a watcher means that it has become increasingly difficult to keep track of the times and channels of programmes which the watcher may wish to view.

It is therefore a still further object of the invention

to provide means whereby this particular problem may ibe overcome.

A still further problem which can arise as a result of the availability of large numbers of channels is that if a second satellite transmission system is to be accessed it may be necessary to have a second receiving dish and a second set of cabling.

It is therefore a still further object of the present invention to overcome this particular difficulty.

According to a first aspect of the present invention there is provided a method of reducing noise in pictures produced from satellite transmissions comprising analysing the picture signal to be displayed, identifying noise signals in said picture signal, and introducing a system generated signal to cover said noise signals.

Preferably, the said system generated signal is produced by comparing the present picture signal with an adjacent picture signal and generating a signal to cover each noise signal based on said adjacent picture signal.

In this way, each noise signal is replaced by a colour signal which corresponds to the colour signal which appeared in that position adjacent the noise signal. In this way the picture definition can be improved.

According to a second aspect of the present invention there is provided apparatus for connecting a plurality of card readers to a satellite transmission decoder module comprising an interface unit for fitment between

said card readers and said decoder module, said interface unit providing automatic switching between said card readers.

According to a further aspect of the present invention there is provided a method of monitoring TV transmissions comprising programming a monitoring device with details of a programme or programmes to be monitored, monitoring available TV channels to locate commencement of the desired programme, and providing an on-screen indication that a monitored programme has been located.

Preferably the on-screen indication is in the form of a channel identification.

Optionally the system may be arranged automatically to select the channel on which the monitored transmission is commencing.

The system may be set up to provide a once only monitoring facility or may alternatively have a repeat monitoring facility.

According to a still further aspect of the present invention there is provided a method of selectively connecting a satellite decoder and receiver arrangement to any one of a plurality of satellite dishes or receiving devices on a single dish via a signal transmission cable connected to said devices via an interface unit.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which:-

Fig. la is a block schematic diagram of a system in accordance with a first aspect of the present invention; Fig. lb is a schematic diagram of a developed embodiment of the first aspect of the invention; Fig. 2a is a schematic diagram of a conventional decoder module and card reader arrangement; Fig. 2b is a schematic diagram of a decoder module and card reader arrangement in accordance with a second aspect of the present invention; Fig. 3a is a schematic diagram illustrating two alternative means of connecting satellite receiver equipment to a satellite dish; and Fig. 3b is a schematic diagram illustrating equipment in accordance with a fourth aspect of the present invention.

Referring to the drawings Fig. la illustrates a system in accordance with a first aspect of the present invention. The system is designed to improve picture quality by covering up a noise signal or sparkle which would appear in the picture with the colour which appeared directly before in that position. As a result of the speed with which the picture is updated this results in a reduced noise element in a displayed picture at any one time but without any significant deterioration in the picture definition. The transmitted signal 1 is received in a normal manner but is then converted to a digital signal by an analogue-to-digital converter 2. The signal is then monitored by a detector device 3 and when a noise signal or sparkle is detected it is sampled a number of times by a sampler 4 which detects its size and position. The noise signal is then replaced by a colour signal as appropriate by a sparkle painter

device 5. This colour is derived by reference to the colour which appeared in the appropriate picture position immediately previous to the appearance of the noise signal. Finally, the signal is reconverted by a digital-to-analogue converter 6 and is subsequently displayed on the TV screen.

In this way the quality of displayed TV signals can be improved in situations where otherwise a significant noise factor might be introduced into a displayed picture.

One example, of the invention is if a sparkle is detected a comparison circuit is used to .analyse the information surrounding the sparkle in order to determine if it is real information or not using the principle of a truth table. Either the sparkle would be ignored or substituted with a piece of information directly before or after or even previously to the sparkle.

The information can be stored and analysed by frame, by line or by portions thereof.

Fig. lb shows a developed embodiment of the first aspect of the invention, including A/D and D/A conversion means, control means, random access memory, comparison means and buffers consituting a delay line for storing successive portions of the picture signal for .analysis and processing prior to output.

Referring now to Fig. 2a a conventional satellite decoder and card reader arrangement is shown.

A card reader 10 has a slot which receives a keycard

which is encoded. On reading the encodement on the card the system will activate the decoding module so as to receive the desired satellite channel. However, any one card will only provide access to a certain number of channels and thus if alternative channels are to be viewed a second card will be necessary. In such a case changing between available channels may necessitate the removal of one card and insertion of another card into the card reader 10. To overcome this problem the system illustrated in Fig. 2b is proposed. In this system two card readers 11 and 12 are provided, each connected to an interface unit 13 which in turn connects to a decoder module 14. Thus a second programme provider using the same encryption system but requiring a different card can be accessed via the second card reader 12 with the interface unit allowing for automatic selection between the card readers as desired. More than two card readers can be connected to the interface unit depending upon the number of cards required.

In a further aspect of the present invention a programme and monitoring unit is included in the satellite system which allows a user to programme the system with information and programmes which they wish to view in the future. The system monitors available transmission channels and when the selected programme is about to commence the indicator on the unit alerts the user to the fact that the programmed channel is about to commence with an item of interest. The system may provide an independent indication of programme or may display the information regarding which channel should be viewed on screen, or indeed may be programmed to change channel to the desired channel automatically. The system can operate with a conventional TV unit,

satellite unit, or indeed with a video recorder. In the conventional TV mode, regardless of which channel is being viewed, the TV screen would display the other channel number which relates to the programme. For example, if the TV is presently tuned to BBC1 and in the pre-programmed programme is on BBC2 a display will appear on the screen with the message "turn to BBC2".

When a satellite system is included in the viewing system the operation would be similar with the desired channel, whether it be on the satellite system or on conventional TV, being displayed with a similar message, such as "turn to BBC1". If a video unit is included in this over-all system then operation may be similar with an on-screen message being displayed even when a video is in the process of playback. The system may be programmable with a once-only facility, whereby the programme cancels once the message has been displayed or alternatively a repeat facility would allow the message to be displayed each time the desired programme appears in the programming schedules. The means of programming the system may be similar to the programming of a video cassette recorder for the automatic recording of transmissions.

A fourth aspect of the present invention will now be described with reference to Figs 3a and 3b. Conventionally, the cable which connects a satellite receiver 20 to the LNB (Low Noise Blockdown Converter) 21 on the dish is a co-axial cable with one centre core and a surrounding screen. The two normal connecting methods are shown in Fig. 3a. In the first method a single voltage signal is sent from the receiver 20 to the LNB 21 and switches on the LNB so the received signal may then travel back down the cable to the

receiver 20. In the second alternative a two-level voltage signal may be sent from the receiver 20 to the LNB 21 which is switchable between two modes depending on which of the two voltage signals it receives and thus the appropriate signal may be received by the receiver 20. In the present invention, regardless of which of these methods is used, a further signal can be transmitted along the cable from the receiver 20 to the dish section. In this case an interface unit 22 can switch between two or more different LNBs 21 on the same dish or between two LNBs on different dishes. Thus the system can switch between different receiving modes. The generation of the signal for operating the interface unit is provided by the receiver 20 with the interface unit 22 provided at the dish. In this way a single cable may be provided between the receiver 20 and the dish or dishes and thus a single cable system can be operated in such a way as to receive transmissions from different satellite systems. The interface control signal for selecting between LNBs/dishes may be a tone signal or a coded pulse type signal.

Various modifications and improvements can, of course, be made to the system described without departing from the scope of the invention. It will also be understood that the above description provides a simple outline of the proposed methods of operation and in practice various further features may be incorporated in the system as necessitated by other functional requirements.