GB2138657A - Near Field Signalling System - Google Patents

Abstract

Apparatus for providing signals for a television receiver comprises an amplifier connected to a video player or computer 1 to receive and amplify the output signal therefrom and connected to feed the amplified signal to a radio frequency transmitting antenna 5. <IMAGE>

Description

SPECIFICATION Signal Transmission The invention relates to the transmission of signals and is, more particularly, a novel method and apparatus for providing video signals for a television set.

The popularity of recorded video entertainment has grown vastly over recent years, to the stage where many homes now possess a video recorder and/or player, by means of which a chosen programme may be displayed on a conventional television set. The programme may have previously been recorded directly by cable from a television channel or may have been purchased in the form of a pre-recorded tape cassette or disc.

In the 'play' mode, the video unit simply monitors the tape or disc, converts the signal to one which is compatible with the input requirements of the television set and feeds the converted signal to the aerial input system of the set.

Video systems have the great advantage of allowing the individual user to select his own programme at will, from an almost unlimited range, and to display it at a time of his own choosing. However, video players/recorders are still fairly expensive and are not normally designed to give a display on several television sets simultaneously. Moreover, even if a suitable player were designed to feed a plurality of television sets, it would be necessary to supply a cable link to each set from the video player.

For this reason, although many hotels now provide a television set in each bedroom, it is not normally possible to provide programmes other than those transmitted by the national television companies. However, it would be desirable to many hoteliers to offer to their guests the option of receiving additional programmes, selected by the guest or the hotelier. Such additional programmes may be purely for entertainment or may be information programmes such as giving hotel news, details of hotel facilities, safety advice or local advertising.

It is therefore one object of this invention to provide a video transmission system which is readily adaptable to remotely supplying prerecorded video programmes to a plurality of television receivers.

The novel method of providing signals for a television set, according to the present invention, comprises amplifying the output signal from a video player or computer and feeding the amplified signal to a radio-frequency transmitting antenna. The apparatus according to the present invention, in its broadest form, comprises an amplifier adapted for connection to a video player or computer to receive and amplify the output signal therefrom and to be connected to feed the amplified signal to a radio-frequency transmitting antenna.

In order for the ultimate user of the invention to put it into practice, he will require, as a minimum, a video player or computer, the amplifier, a radio frequency transmitting antenna and, of course, at least one television receiver. However, the invention may take advantage of those components which he already has in his possession and therefore the equipment which is offered for purchase by the ultimate user may take various forms. Thus, as already indicated, the apparatus of the present invention in its broadest form is an amplifier suitably adapted to receive and amplify the video player or computer output signal and to feed the amplified signal to the transmitting antenna.Where, as indicated below, a pre-amplifier is included in the circuit between the video player or computer and the main amplifier, the pre-amplifier may be incorporated in the unit offered for sale. For example, a preamplifier may be incorporated in the cable connector by means of which the feed cable to the main amplifier is attached to the video player or computer output socket.

The transmitting antenna may similarly be incorporated in the unit which includes the main amplifier.

In yet another version of a unit which may be offered to the user as a feature of the present invention, a video player dedicated to the invention may be combined with an amplifier as described above in a single piece of equipment, which may be designed to be- portable and which may, if desired or expedient, incorporate the radio-frequency transmitting antenna.

For the convenience of the domestic user in particular, the apparatus according to the present invention may be combined with facilities for normal television reception, so that the user does not have to rearrange the cable connections to his receiver and video player according to his current need. Thus a unit may be offered for sale which comprises a cable connector for attachment to a video player output socket, which cable connector may incorporate a pre-amplifier and which is linked by cable to the amplifier unit, said amplifier unit having two signal outputs, one to feed a radio frequency transmitting antenna and the other to a conventional television receiver.By means of such a unit, the user may choose between normal television reception and video-produced television display, while at the same time having the option of transmitting a selected videoproduced signal to a separate television receiver, for example in another room.

It is worth emphasising at this stage that the output of most video players and computers available in the UK and abroad is at a frequency (600 MHZ) corresponding to that of Channel 36 of the normal UHF band of channels. Since this channel lies outside the channel groups normally used for television purposes, there is no danger of interference between a radio-transmitted signal derived from a standard video player or computer, as arises according to the present invention, and the television signals available in the surrounding area. The standard Channel 36 frequency therefore has certain attractions.However, in order to avoid transmissions created in apparatus of the present invention "swamping" or otherwise impeding displays produced by other similar apparatus, for example displays produced by video game units (which also tend to use Channel 36) or by another home computer, it is preferred that the video player be tuned to an adjacent channel, for example Channel 35, 37 or 38. The adjacent channel selected should take account of the channels used by other transmission in the surrounding area.

In accordance with the present invention, the output signal of the video player or computer is fed to the amplification stage or stages.

Advantageously, the signal is fed via a high-pass filter, for example a high-pass transformer, by means of which extraneous undesired signals may be eliminated before the desired signal is amplified.

For maximum benefit, the amplification of the video or computer signal is achieved in at least two stages. Thus the signal may firstly be amplified in a pre-amplifier, which may advantageously be a narrow-band amplifier preset to the frequency band corresponding to the video player or computer output. The preamplifier may be so pre-selected as to give a gain within the range from 10 to 20 dB, especially at least 12 dB, for example. Typically, a video player or computer output of the general order of about one miliivolt, especially less than 1.5 mv, may be amplified in the pre-amplifier to an output of the general order of about 10 mv.

Before the signal from the pre-amplifier is fed to the main amplifier, it may if desired be combined with one or more other signals intended for transmission. Thus the signal arising in a video player may if desired be combined with a normal television signal picked up by a suitable aerial and converted to a different channel, before the combined signals are amplified in the main amplifier and subsequently transmitted together to a remote receiver.

The main amplifier, especially if it is to be used to amplify combined video and television signals as aforesaid, may usefully be a wide-band amplifier, of which the gain will vary according to the frequency of the signal being amplified. After amplification, the signal may be delivered at a level of the general order of about 250 mv, up to a maximum of about 1200 mv, to the radiofrequency transmitting antenna.

The transmitting antenna may be a conventional dipole loop aerial, which advantageously is tuned to the frequency, or frequencies, of the signals to be transmitted.

Since the signal or signals is likely to be at a frequency, say Channel 35, significantly different from that of any television signals receivable in the surrounding area, there is no risk of interference with such signals. However, the quality of the subsequent reception may be enhanced if the transmitted signals arising from the system according to the present invention are polarised in a different direction from the main receivable transmissions, e.g. vertically as opposed to horizontal polarisation.

The invention will now be further described by reference to the accompanying drawing, which illustrates diagrammatically one embodiment of a video transmission system according to the present invention.

Referring to the drawing, the output from a conventional video recorder/player 1, delivering a signal of 1 mv at Channel 38 frequency, is fed via a high-pass transformer 2 to a pre-amplifier 3, pretuned to that frequency, by means of which the signal is amplified to 8 mv.

The signal from the pre-amplifier 3 is then amplified in a main amplifier 4, which delivers a signal of 250 mv to a dipole loop aerial antenna 5, by means of which the signal is transmitted to one or more remote receivers, not shown.

Power to drive the pre-amplifier 3 is provided at 12 v D.C. by the main amplifier 4. The power is transmitted from the main amplifier to the preamplifier via the co-axial cable link which in the reverse direction feeds the radio-frequency signals from the pre-amplifier to the main amplifier.

In experimental trials using the illustrated system, I have successfully transmitted prerecorded video programmes and received stable, strong pictures in hand-held portable television receivers, fitted with simple loop aerials.

When the apparatus according to the present invention, for example that shown in the drawings, is used for example in a hotel, such that a single transmission supplies programmes to a variety of rooms, it is desirable that the transmissions be self-confined to within the limits of the buildings. This may readily be achieved by appropriate design of the transmitting antenna and/or limiting the output signal, and/or by the provision of suitable deflectors.

When, for example in the illustrated embodiment, the video player 1 is replaced by a computer, the visual display on that computer may, by means of the present invention, be shown simultaneously on one or more other visual display screens, without the need for a direct cable connection from the originating computer to those screens.

Claims (8)

1. Apparatus for providing signals for a television receiver comprising an amplifier adapted for connection to a video player or computer to receive and amplify the output signal therefrom and to be connected to feed the amplified signal to a radio-frequency transmitting antenna.

2. Apparatus as claimed in claim 1, incorporating a pre-amplifier between said connection to a video player or a computer and the amplifier.

3. Apparatus as claimed in claim 2, wherein said pre-amplifier is incorporated in the cable connector by means of which the connection is made to the video player or computer output socket.

4. Apparatus as claimed in any of the preceding claims, incorporating a video player and said amplifier in a single unit.

5. Apparatus as claimed in any of the preceding claims, incorporating also said radiofrequency transmitting antenna.

6. Apparatus as claimed in any of the preceding claims, incorporating also means to feed a received television signal direct to a television receiver.

7. Apparatus for providing signals for a television receiver, substantially as hereinbefore described with reference to; and as illustrated in, the accompanying drawing.

8. A method of providing signals for a television receiver, comprising amplifying the output signal from a video player or computer and feeding the amplified signal to a radio-frequency transmitting antenna.