GB2247375A - Domestic audio/visual entertainment system - Google Patents

Abstract

With an increase in the number of video entertainment systems, such as video recorders. video disc players and satellite receivers, producing their signals in channels 35 to 38, interference becomes likely when a number of such devices are connected to a television. An audio-visual entertainment system comprises a television 1, a video recorder 3 and other local video signal sources, such as satellite receivers 7 and 8, and having a routing system 16 allows a large number of video sources to be used in an audio-visual entertainment system without interference occurring. <IMAGE>

Description

DOMESTIC AUDIO/VISUAL ENTERTAINMENT SYSTEM.

The present invention relates to a domestic audio/visual entertainment system.

In recent years, the number of electronic devices for connection to a conventional television receiver has progressively increased with the introduction of video cassette recorders and, more recently, direct broadcast by satellite receivers. At the present time, two direct broadcast satellites are in operation and require the provision of two separate receivers for converting the satellite broadcast signals into a form suitable for supply to a domestic television receiver.

Figure 1 illustrates a typical domestic audio/visual entertainment system. A conventional television receiver 1 has a UHF input 2 for receiving UHF signals from various sources. The input 2 is connected to the output of a video cassette recorder 3, which has a UHF input 4 connected to the output of an Astra satellite receiver 5.

The receiver 5 is connected to a dish-type aerial 6 for receiving microwave signals broadcast by the Astra satellite. The receiver 5 also has a UHF input 7 connected to a BSB satellite receiver 8. The receiver 8 is connected to an aerial 9 of the dish or square type for receiving microwave broadcasts from the BSB satellite. The receiver 8 also has an input 10 for connection to a conventional UHF aerial 11 for receiving terrestrially broadcast television signals.

In order for the video cassette recorder (VCR) to be able to record signals from all of the sources, it has to be connected downstream of the satellite receivers 5 and 8 and the aerial 11. For convenience in order to avoid using split cables, the aerial 11 is connected upstream of the receivers 5 and 8 so that the signals from the aerial 11 pass through the receivers 8 and 5 to the VCR 3 for recording terrestrial broadcasts and through the VCR 3 to the television 1 for viewing terrestrial broadcasts.

In order to allow the television receiver 1 to be tuned conventionally, the VCR 3 incorporates a modulator which, during playback of a video cassette, converts the video signals to UHF Channel 36. Similarly, the BSB satellite receiver 8 converts the microwave signals from the aerial 9 into UHF signals on Channel 38. The VCR can be preset so as to be able to record signals on Channel 38 in order to allow the BSB television signal to be recorded for subsequent playback. The Astra satellite receiver 5 likewise incorporates a modulator and converts the signals from the aerial 6 into UHF signals.

A problem arises because of the limited band width available in the UHF bands allocated to terrestrial television broadcasting. Figure 2 of the accompanying drawings illustrates this. Bands 21 to 34 and 39 to 68 are allocated to terrestrial television transmitters and, at present, broadcast four network television channels in the U.K. Television receivers 1 are capable of tuning to any of bands 21 to 68 so that the television receivers can be used without modification anywhere within the U.K.

Channels 35 to 38 are not at present allocated to any terrestrial broadcaster. It is therefore convenient for VCR's and satellite receivers to "re-transmit" their signals in the free channels so that the VCR's and satellite receivers can likewise be sold for use anywhere in the U.K. without requiring modification.

As shown in Figure 2, each channel has a band width of 8 MHz and the terrestrial broadcast television signals are band-limited to about 6.5 MHz so as to fit within the channel allocation without interfering with signals in adjacent channels. Thus, in theory, the gap between channels 34 and 39 is sufficiently large to accommodate four locally-generated UHF television signals.

However, a problem arises because the UHF modulators incorporated into VCR's and satellite receivers occupy more than the band width allocation for each channel. In particular, terrestrial broadcasters suppress one of the side bands of the UHF signals so as to ensure that the band width of the transmitted signal falls sufficiently well within the frequency limits of the allocated channel. However, the modulators in VCR's and satellite receivers are somewhat less sophisticated and do not suppress one of the side bands. Thus, the band width of each UHF signal coming from the VCR's and satellite receivers is of the order of 12 MHz and thus strays outside the nominal broadcast channel band limits.

Accordingly, although the gap in the UHF broadcast band is theoretically large enough to accommodate four additional channels, in practice this cannot be achieved and, in fact, there is room only for two locally generated UHF signals between channels 34 and 39 if interference effects are to be avoided.

The system shown in Figure 1 therefore has the problem of finding room for the UHF output of the Astra satellite receiver 5. It is believed that such receivers will have modulators tuned to channel 36 but, since the VCR 3 already produces its UHF output at channel 36, interference is inevitable.

A further problem is that the proposed new fifth terrestrial broadcast television network is intended to be broadcast in channels 35 to 38. If and when this network begins broadcasting, interference problems with locally generated UHF television signals may well preclude the use of an arrangement of the type shown in Figure 1.

It is known to use SCART connectors on television receivers and VCR's for interconnection purposes so that video signals in the form of colour component video, colour difference component video, or encoded composite video signals are supplied from the VCR directly to the video circuits of the television receiver. Similarly, it is known to provide SCART outputs on satellite receivers to permit direct connection to television receivers.

However, no switching means are provided and, in order to accommodate the various sources illustrated in Figure 1, repeated disconnection and reconnection of SCART cables and connectors would be necessary in order to allow any source to be viewed or recorded.

According to the present invention, there is provided a domestic audio/visual entertainment system, comprising a television, a video recorder, at least one source of video signals and a signal routing system, the signal routing system comprising first switch means for selectively routing a video signal from any one of the video recorder and the or each video signal source to the television and second switch means for selectively routing a video signal from the video signal source or any one of the video signal sources to the video recorder.

As used herein, the term "video signal" is defined to mean a signal occupying the video band of frequencies as distinct from a modulated radio frequency signal, for instance in the UHF bands. Thus, video signals include colour component signals such as RGB, colour difference, and SVHS signals, and encoded composite video signals such as PAL-encoded signals (the U.K. standard) and baseband video signals.

The problems of using "free" channels in the UHF broadcast bands and avoiding interference between UHF signals is thus avoided. Any number of video signal sources, such as satellite receivers, can be accommodated. Any source, including terrestrial broadcasts, can be viewed by means of the television and likewise the VCR may record from any source including terrestrial broadcasts. A terrestrial aerial has to be connected to both the television receiver and the VCR to permit viewing and recording of terrestrial signals, but all locally generated television signals are routed as video signals.

In order to permit the use of such a system with a television receiver of the type not having a SCART connector or any other suitable access to the video circuits of the television, a UHF modulator may be connected between the output of the first switch means and an aerial input of the television. such an arrangement requires the use of a single UHF channel, such as channel 36, for viewing purposes but all routing is still performed on video signals.

The video signal sources preferably include at least one satellite receiver but may include other types of source, such as video cameras and cable television signals.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block schematic diagram of a known entertainment system as described hereinbefore, Figure 2 is diagram illustrating the allocation of terrestrial television broadcast channels; Figure 3 is a block schematic diagram of an entertainment system constituting a first embodiment of the invention; and Figure 4 is a block schematic diagram of an entertainment system constituting a second embodiment of the invention.

The same reference numerals refer to like parts throughout the drawings.

The television 1 shown in Figure 3 has its UHF aerial input 2 connected to a UHF output 12 of the VCR 3, whose UHF input 13 is connected to the terrestrial UHF aerial 11. The television receiver 1 also has a SCART connector 14 which provides a two-way signal connection to a SCART connector 15 of a routing system 16. The VCR 3 has a SCART connector 17 which provides a two-way signal connection to a SCART connector 18 of the routing system 16.

The SCART interconnection system provides the bidirectional flow of audio, video, and control signals, the audio being in the form of left and right stereo signals and the video being in the form of colour component signals as well as composite video base band signals (PAL encoded signals in the U.K). The SCART connections between the VCR 3 and the routing system 16 and between the television receiver 1 and the routing system 16 make use of the bi-directional capability of this standard, whereas the other SCART connections shown in Figure 3 pass signals in a single direction only.

The Astra satellite receiver 7 has a SCART connector 19 connected to an input 20 of the routing system 16. Likewise, the BSB satellite receiver 8 has a SCART connector 21 connected to an input 22 of the system 16.

The routing system 16 is illustrated diagrammatically in terms of signal flow in Figure 3. In particular, each signal line in practice comprises a plurality of conductive paths corresponding to the various SCART signals making up each communication pathway.

The routing system 16 includes a first switch means 23 whose output is connected to the SCART connector 15 of the system and thence to the SCART connector 14 of the television receiver 1. The first switch means 23 are embodied as a plurality of electronic switches arranged, in the embodiment shown, as a three-way changeover switch. Thus, the first switch means 23 has respective inputs connected to receive selectively the video signals from the receiver 8, the receiver 7, and the VCR 3.

Similarly, second switch means 24 are provided for selectively routing video signals from the television receiver 1 and the receivers 8 and 7 to the input of the VCR 3.

The entertainment system shown in Figure 1 thus permits the television receiver 1 to receive signals from any of the sources generating local video signals and from the terrestrial aerial 11. Simultaneously, the VCR can record video signals from the receivers 1, 7 and 8 and from the aerial 11. The connection from the television receiver 1 to the VCR 3 via the switch means 24 allows direct recording from the television receiver. This has advantages in that the tuner of the television receiver is often of better quality than the tuner of the VCR.

Also, a VCR not equipped to receive NICAM sound signals can nevertheless receive stereo sound signals from a television receiver equipped with a NICAM decoder. Although the VCR 3 may continue to supply UHF signals on channel 36 during playback, these need not be used by the television receiver 1 as the replayed video signals are routed via the routing system 16. Although the satellite receivers 7 and 8 may also generate UHF signals, these are not used in the entertainment system shown in Figure 3 so that the danger of interference between UHF signals is eliminated.

Any number of video signal sources may be routed by expanding the routing system 16 by adding additional SCART inputs and additional ways to the first and second switch means 23 and 24. Additional VCR's may also be provided by adding additional SCART connectors and second switch means. Likewise, additional television receivers may be added by adding further SCART connectors and first switch means. Thus, the entertainment system can be expanded as necessary in order to incorporate any number of television receivers, VCR's, satellite receivers, and other sources such as video disc players, video cameras, and cable television signals.

Although all modern video sources such as VCR's and satellite receivers are provided with SCART connectors, not all existing television receivers have SCART connectors. Accordingly, in order to accommodate television receivers without SCART connectors, the entertainment system shown in Figure 4 may be used. The routing system 16 of Figure 4 differs from that of Figure 3 essentially in that a UHF modulator 25 is connected between the first switch means 23 and a UHF output 26 for the television receiver 1. For convenience, the terrestrial aerial 11 is connected to a UHF input 27 of the routing system 16 so that the output of the modulator 25, for instance on channel 38, is added to the terrestrial broadcast signals received by the aerial 11.

The UHF output 26 is connected to the UHF input 13 of the VCR 3, whose UHF output 12 is connected in the conventional manner to the UHF aerial input 2 of the television receiver 1. Thus, the entertainment system shown in Figure 4 requires the use of one of the free channels in the UHF broadcaster television bands to permit any number of sources to be viewed.

Although not generally available at present, it may be that further types of video recorder, such as video disc recorders and players, become available in the future.

Such recorders may be connected in the same way as the VCR 3 shown in Figures 3 and 4.

It is thus possible to provide an entertainment system which can accommodate any number of video signal sources without restrictions caused by numbers of free channels in the UHF broadcast television bands and without creating any interference problems.

Claims (11)

1. An audio-visual entertainment system, comprising a television, a video recorder, at least one source of video signals and a signal routing system, the signal routing system comprising first switch means for selectively routing a video signal (as hereinbefore defined) from any one of the video recorder and the or each video signal source to the television and a second switch means for selectively routing a video signal from any one of the video signal sources to the video recorder.

2. An entertainment system as claimed in Claim 1, in which the second switch means is arranged to selectively route a video signal from the television to the video recorder.

3. An entertainment system as claimed in any one of Claims 1 and 2, in which a UHF modulator is arranged to modulate the output of the first switch means.

4. An entertainment system as claimed in any one of the preceding claims, in which at least one video signal source is a satellite receiver.

5. An entertainment system as claimed in any one of the preceding claims, in which video signals are conveyed between at least two elements of the system via a SCART connection.

6. An entertainment system as claimed in any one of the preceding claims, in which, in use, a UHF input of the video recorder receives signals from terrestrial broadcast transmitters.

7. An entertainment system as claimed in any one of the preceding claims, in which the first switch means is electronic.

8. An entertainment system as claimed in any one of the preceding claims, in which the second switch means is electronic.

9. An entertainment system as claimed in any one of the preceding claims, including a further video recorder.

10. An entertainment system as claimed in any one of the preceding claims, including a further television.

11. An entertainment system substantially as hereinbefore described with reference to and as illustrated in Figures 3 and 4 of the accompanying drawings.