Communication system

Abstract: A communication system has a plurality of transmitters (12A,12B) and receivers (14A,14B). Each transmitter can send messages for receipt by receivers (14). At least one transmitter (12) can send first type messages for receivers not individually identified in the message, or second type messages which include identification of a recipient receiver. An alarm message, such as a message to alert deaf users to a first alarm, can therefore be sent as a first type message, whereas a paging signal to a specific person can be sent as a second type message.

Description: The present invention relates to communication systems and particularly, but not exclusively, to systems for facilitating communication with people having impaired hearing. Among the difficulties presented by impaired hearing, is the problem that sufferers cannot hear alarms sounding, such as fire alarms. In consequence, they may be placed at physical risk even though otherwise able-bodied, merely because they are not alerted sufficiently quickly, or at all. They may not realise that an evacuation is under way, for instance as a result of a fire. The present invention seeks to address these difficulties. GB2217149 describes a communication system having a group of receivers associated with a centrally located base station. Channel access protocols allow data traffic to be suspended, when appropriate, to allow voice communication. US4103286 describes a system providing a group call capability for a digital pager. The invention provides a communication system having a plurality of transmitter means and at least one receiver means, the transmitter means being operable to transmit messages for receipt by the or each receiver means, and the or each receiver means being operable to receive messages transmitted by the transmitter means, the plurality of transmitter means being operable to transmit a message of a first type which does not individually identify the or one of the receiver means in the message, whereby the or each receiver means may respond to a message of the first type when within range of any of the said transmitter means, and at least one of the transmitter means being further operable to transmit a message of a second type to which the or one of the receiver means will respond only if sent from designated transmitter means with which that receiver means is associated. Consequently, if a deaf person carries a receiver which responds to first type messages, they can be alerted whenever they are within range of a transmitter means which can send first type messages, but it is not necessary for those initiating the transmission of the message to know the identity, location or even the presence of the person carrying that receiver. The general purpose message of the first type therefore performs in a manner similar to a general purpose announcement over a public address system. Second type messages, however, identify the intended recipient and can therefore be used for private messages. Preferably at least one receiver means is operable to detect identification information contained in a message and to respond to all messages received which are of the first type and to any received message which is of the second type and which identifies that receiver means as the intended recipient. There may be at least one receiver means which is operable to detect identification information contained in a message and to respond only to all messages received which are of the first type. There may be at least one receiver which is operable to detect identification information contained in a message and to respond only to a received message which is of the second type and which identifies the receiver means as the intended recipient. The messages are preferably transmitted as radio signals and preferably all of the transmitter means transmit at least first type messages on the same frequency. Each transmitter means may transmit second type messages on a respective frequency. Second type messages may be transmitted after encoding in a manner unique to the transmitter means in use. Preferably the transmitters are each operable to transmit messages of the first and of the second type. Messages may be digitally encoded and preferably include label data winch identifies the intended recipient receiver means or identifies the message as a message of the first type. A message of the first type may include identification of the message as a message of the first type. A message of the first type may be identified by the state of an identifying bit. At least messages of the second type may include message data. Preferably at least one receiver means is operable in receipt of a first message to alert a user in a substantially non-audible manner. The said one receiver means may be operable to vibrate to alert a user. The invention also provides transmitter means for use in the system defined above, characterised by the transmitter means being operable to send first type messages which do not individually identify a receiver means in the message, whereby any receiver means may respond to a first type message when within range of the transmitter means, and further characterised in that the transmitter means is operable to send second type signals in a manner unique to the said transmitter, whereby receiver means may only respond to a second type message if the transmitter means is the designated transmitter means with which that receiver means is associated. The invention also provides receiver means for use in the system defined above, characterised in that the receiver means are operable to respond to first type signals which do not individually identify a receiver means in the message, whereby the receiver means may respond to a first type message when within range of any transmitter means of the system, and further characterised in that the receiver means are associated with a designated transmitter means of the system, and are operable to receive second type signals only from the designated transmitter means and sent in a manner unique to the designated transmitter means. Examples of a system according to the present invention will now be described in more detail, by way of example only and with reference to the accompanying drawings in which: Fig. 1 is a highly schematic diagram of a communication system according to the present invention; Fig. 2 is a schematic diagram of the internal workings of a transmitter for use in the system of Fig. 1 ; Fig. 3 is a schematic of a digital message for use in the system of Fig. 1; and Fig. 4 is a schematic diagram of the internal workings of a receiver for use in the system of Fig. 1. The communication system 10 shown in the drawings, particularly in Fig. 1, comprises a plurality of transmitter means 12A,12B and a plurality of receiver means 14A,14B. Each transmitter means 12 is operable to transmit messages for receipt by receiver means 14. Each receiver means is operable to receive messages transmitted by transmitter means 12. At least one of the transmitters 12 is operable to transmit a message of a first type for receiver means which are not individually identified in the message, or of a second type which includes identification of the intended recipient receiver means. At least one receiver means 14 is operable to respond to received messages, as will be described. Before describing the operation of the system in more detail, it is appropriate to describe the construction of transmitters and receivers in more detail, and to describe the nature of a message signal used in the system. Fig. 2 shows a radio transmitter 12 having transmitter circuits 16 driving an aerial 18 in a manner which may be conventional in itself. The signal to be transmitted is supplied to the transmitter circuit 16 by encoding circuits 20, which may be largely software controlled. Control circuits 22 allow users to control operation of the transmitter, and may include keyboards, displays or automatic systems connected, for instance, to fire alarm circuits or the like. The transmitter 12 can send one of two types of message. These are digitally encoded. The general format of digital packets which form these messages is shown in Fig. 3. Fig. 3 shows a horizontal line divided into sections representing individual bits forming part of the message and sent serially, with the left-hand most bit sent first, followed by bits further to the right in the drawing. The total number of bits in a message, and the manner in which they are used can be chosen according to any desired protocol chosen in accordance with the particular application of the system. In the message shown in Fig. 3, a first group of bits comprises a "header" 24, followed by a group of message data bits 26. The contents of the header serve to identify whether the message is of the first or second type. If the message is of the first type, an alarm bit 28 is set (or, alternatively, left unset) to flag this. The remainder of the header is then not of significance. An alarm bit 28 may be accompanied by message data within the group 26 (such as data identifying the nature of an emergency), depending on how the receiver 14 is expected to interpret a message of the first type. If the message is to be of the second type, the alarm bit 28 is not set (or, in the alternative, is set), but the remainder of the header incorporates appropriate bits to identify a specific receiver which is the intended recipient of the message. In this case, a message will usually be incorporated in the message group 26. Fig. 4 shows a receiver 14 in more detail. A radio aerial 30 drives receiver circuits in a manner conventional in itself. The output of the receiver circuit 32 is decoded at 34 by means which may be controlled by hardware, software or a mixture of the two. Having decoded a message, the decoder 34 controls output devices shown in Fig. 4 as a vibrating mechanism 36, and a display 38. The overall operation of the communication system shown in Fig. 1 can now be described in more detail. Initially in this explanation, it is assumed that all transmitters 12 can send messages of the first or second type, and all receivers can receive both types of message. Other alternatives will be described later. The transmitter 12A may be located at an appropriate location, such as in a public building 40A. The transmitter 12B is likewise installed, such as in a public building 40B. A deaf or hearing-impaired person (referred to hereafter simply as a "deaf person", for simplicity) will carry one of the receivers 14. Another deaf person can carry another receiver. In principle, it is envisaged that there need be no limit on the number of transmitters or receivers in the system. It is envisaged that at least for first type messages, all transmitters and all receivers will operate on the same frequency, or at least that substantially all receiver means are operable to receive first type messages transmitted by substantially all of the transmitter means. If a fire alarm arises in one of the buildings, say 40A, the transmitter 12A will transmit a message of the first type, and may do so repeatedly. Any receiver 14 within range of the transmitter 12A, particularly any within the building 40A, will receive that message. The decoder 34 will recognise the message as a message of the first type, by checking the alarm bit 28. Upon detecting a message of the first type, representing an alarm of some form, the decoder 34 will activate the vibrating mechanism 36. This serves to alert the deaf person, who will be unable to hear conventional fire alarms which may also be sounding. The deaf person can then immediately leave the building, or seek assistance. If the first type message includes message data within the group 26, this can be decoded and displayed at 38. This allows the nature of the alarm to be identified to the user, e.g. as a fire alarm, bomb alert etc., so that appropriate action can be taken. It is envisaged that by providing a connection between the control circuits 22 of the transmitter 14, and fire alarm and other systems, a first type message can be sent immediately when the alarm is activated, so that a deaf person is alerted as quickly as a hearing person. The presence of the alarm bit 28 in the first type message causes all receivers 14 within range of the transmitter 12A to receive and act on the first type message. Consequently, any deaf person carrying one of the receivers and within range of the transmitter 12A will be alerted, whether or not those in charge of the building are aware of their presence, identity or location. Consequently, in a hotel for instance, it is envisaged that it may be unnecessary to make special arrangements to evacuate a deaf person in the case of a fire, so long as the hotel is equipped with one of the transmitters 12, and the deaf person is equipped with one of the receivers 14. Moreover, since all receivers can preferably receive first type signals from all transmitters, a deaf person will know that their receiver will work in any other building equipped with the system, without them needing to take any special steps or alert those in charge of that building of their presence or identity. It is thus envisaged that the system can greatly enhance the personal safety of a deaf person without necessitating any loss of privacy. In addition to use in emergencies, as described above, the ability to send second type messages allows the system to be used to send private messages to a specific user. In this case, a transmitter 12 would be instructed with the identity of the user, and the message to be sent. A message packet would then be made up by the encoder circuits 20. This would include an identifying sequence of bits in the header 24, but no alarm bit 28. The message to be sent would be encoded into the message group 26. When the resultant message is transmitted, all receivers 14 within range will receive it, but all receivers other than the receiver identified by the header will ignore the message upon decoding it and finding that it has neither an alarm bit nor their own identifying data. However, the intended recipient receiver will decode the header 24 to discover that although the alarm bit 28 is not set, the identifying data identifies it. The message in the group 26 can then be decoded and displayed at 38. The user can be alerted to the existence of a message by operation of the vibrating mechanism 36. The system can be further enhanced, for instance by installing a transmitter 12 at the home or place of work of the deaf person. That transmitter 12 could be connected to fire alarms etc. as described above, and also to door bells, telephones or other equipment. Thus, by carrying a single receiver at all times, a deaf user would be alerted at home to the door bell or telephone ringing, and while out in a public building, would be alerted to a fire alarm or other emergency. The principal safety advantages arise from the ability to send messages of the first type from substantially all transmitters to substantially any receiver within range. However, the practical versatility of the system is greatly enhanced by the ability to send messages to specific users. This enhances communiation with a deaf user, but can also be used to enhance communication with a hearing user. A hearing user may carry a receiver 14 which can be used in the same manner to alert them to emergencies, or to receive messages intended for the specific user. It may be that in some cases, hearing users can dispense with the facility to receive first type messages, or that deaf users may dispense with the ability to receive second type messages. However, it is envisaged that in order to be fully effective, all transmitters should normally be expected to transmit at least first type messages, and all receivers to receive them. The ability to send second type messages allows a building to enhance communication with all staff, by the paging nature of the second type messages, while also enhancing the safety of deaf users. It may be appropriate for each transmitter to send second type signals on a unique frequency, or encoded in a unique manner. The transmitter would have one or more associated receivers to which it is a "home" transmitter and which are equipped to receive at the unique frequency or decode in the appropriate manner. In that way, the system can provide private paging facilities, e.g. for employees of a business, while still providing emergency assistance for deaf persons, including deaf visitors and deaf employees. A receiver would receive second type messages only from its "home" transmitter but first type messages from any transmitter. It is realised that on occasions, a receiver might be within range of more than one transmitter and that this might give rise to false alarms, e.g. a first type message received from a neighbouring building. However, it is considered that any inconvenience which results would be acceptable in the light of the advantages accruing from the universality of the system. It will be apparent that many variations and modifications can be made to the apparatus described above, without departing from the scope of the present invention. In particular, the details of circuits, transmission encoding techniques etc. can be widely varied in accordance with the technology chosen for the system. One possible arrangement is for all transmitters to operate on a single frequency but for the header to include a system address identifying the transmitter. Receivers can then ignore second type messages unless received from their "home" transmitter, but can receive a first type message from any transmitter. This arrangement allows a second type message to be sent to the whole group of receivers to which a transmitter is "home", or the header could include additional data specifying one or more of the group.

Claims: A communication system (10) having a plurality of transmitter means (12) and at least one receiver means (14), the transmitter means being operable to transmit messages for receipt by the or each receiver means, and the or each receiver means being operable to receive messages transmitted by the transmitter means, the plurality of transmitter means being operable to transmit a message of a first type which does not individually identify the or one of the receiver means in the message, whereby the or each receiver means may respond to a message of the first type when within range of any of the said transmitter means, and at least one of the transmitter means being further operable to transmit a message of a second type to which the or one of the receiver means will respond only if sent from designated transmitter means with which that receiver means is associated. A system according to Claim 1, characterised in that at least one receiver means (14) is operable to detect identification information (24) contained in a message and to respond to all messages received which are of the first type and to any received message which is of the second type and which identifies that receiver means as the intended recipient. A system according to Claims I or 2, characterised by comprising at least one receiver means (14) which is operable to detect identification information (24) contained in a message and to respond only to received messages which are of the first type. A system according to Claims 1, 2 or 3, characterised in that at least one receiver means (14) is operable to detect identification information (24) contained in a message and to respond only to a received message which is of the second type and which identifies the receiver means as the intended recipient. A system according to any preceding Claim, characterised in that the messages are transmitted as radio signals. A system according to any preceding Claim, characterised in that all of the transmitter means (12) transmit at least first type messages on the same frequency. A system according to any preceding Claim, characterised in that each transmitter means (12) transmits second type messages on a respective frequency. A system according to any preceding Claim, characterised in that second type messages are transmitted after encoding in a manner unique to the transmitter means (12) in use. A system according to any preceding Claim, characterised in that the transmitter means (12) are each operable to transmit messages of the first and of the second type. A system according to any preceding Claim, characterised in that messages are digitally encoded. A system according to Claim 10, characterised in that messages include label data (24) which identifies the intended recipient receiver means (14) or identifies the message as a message of the first type. A system according to Claim 11, characterised in that a message of the first type includes identification of the message as a message of the first type. A system according to Claim 11 or 12, characterised in that a message of the first type may be identified by the state of an identifying bit (28). A system according to any preceding Claim, characterised in that at least messages of the second type include message data (26). A system according to any preceding Claim, characterised in that at least one receiver means (14) is operable in receipt of a first type message to alert a user in a substantially non-audible manner. A system according to Claim 15, characterised in that the said one receiver means (14) is operable to vibrate to alert a user. Transmitter means (12) for use in the system (10) of any preceding claim, characterised by the transmitter means being operable to send first type messages which do not individually identify a receiver means in the message, whereby any receiver means may respond to a first type message when within range of the transmitter means, and further characterised in that the transmitter means is operable to send second type signals in a manner unique to the said transmitter, whereby receiver means may only respond to a second type message if the transmitter means is the designated transmitter means with which that receiver means is associated. Receiver means (14) for use in the system (10) of any of claims 1 to 16, characterised in that the receiver means are operable to respond to first type signals which do not individually identify a receiver means in the message, whereby the receiver means may respond to a first type message when within range of any transmitter means of the system, and further characterised in that the receiver means are associated with a designated transmitter means of the system, and are operable to receive second type signals only from the designated transmitter means and sent in a manner unique to the designated transmitter means.

Inventors: COLDICOTT MARTYN, HASELDINE STEPHEN, COLDICOTT, MARTYN, HASELDINE, STEPHEN, Coldicott, Martyn c/o Evets Communications Ltd., Haseldine, Stephen c/o Evets Communications Ltd.
Applicants: DEAF ALERTER PLC
Application year: 1996
Main classification: G08B1
IPC codes: G08B1