GB2208984A - Control of RDS data by supervisory transmissions - Google Patents

Abstract

In a radio data system a transmitter broadcasts its own first service, identified by its service number, and transmits digital codes as well as programme material. The codes include other Network (ON) codes which provide information about other networks e.g. receivable local stations, and include the service numbers of the other networks to which they pertain. A second transmitter station receiving such ON codes can respond to those which have its particular service number by updating its own RDS information which includes codes pertaining to itself and by responding to those with other service numbers to assemble and transmit on ON codes which relay the received codes, including the service numbers. This allows ON information to be reconstructed off the air, and allow simplification of fixed inter-transmitter links.

Description

IMPROVED RADIO DATA SYSTEM The present invention relates to radio data systems in which various digital codes are superimposed on the audio programme material and is conceived within the framework of the proposals in the European Broadcasting Union (EBU) RDS Specification, Doc. Tech.

3244-E.

Among the codes to be employed are TP which indicates that a programme is a traffic programme, i.e. it carries traffic announcements, and TA which indicates that a traffic announcement is currently being made.

The TP code is simply a flag to indicate that the present tuned programme carries traffic announcements. A receiver may respond to this flag by switching on an LED or giving an indication on an LCD display.

The TA code is also a flag to indicate that a traffic announcement is currently present and may initiate the following receiver responses: Normal Reception Mode - Increase volume for the duration of an announcement.

Cassette Playing Mode - Switch to radio for duration of the announcement, and switch back to cassette afterwards.

Audio Muted Mode - Switch to Normal Reception Mode for duration of announcement, and switch back to Muted Audio afterwards.

The TP and TA signals correspond to identical features of the AR1 system which has been in use in some European countries for some years.

In order to reduce the acquisition time for TA (especially during interference), the relevant RDS group (Group 15) should be transmitted eight times immediately after each switching of TA (On or Off).

Other RDS codes of interest are as follows. Programme identification (PI) codes are essential to assist automatic tuning of RDS receivers. Alternative frequency (AF) codes provide lists of alternative frequencies associates with a particular PI code. PTY and PIN provide programme type and programme identification number respectively.

The Other Network (ON) information feature is intended to allow updating of AF, PTY, TP, TA and PIN information for networks other than that to which receiver is at present tuned. That is, it is intended to allow the broadcaster to cross-reference information about all his networks and indeed, if mutual agreement can be reached, about the networks of other broadcasters.

Of this information, which can be cross-referenced via the ON feature, the most important are the AF information for Other Networks and the TP, TA traffic feature. Either, or both, of these features may be utilised even where the other information (PTY and PIN) is not used on either the received network (i.e. that of the tuning frequency) or Other Networks.

The basic function of ON information is to assist automated tuning to other networks. Thus the ON information enables the AF lists for all pushbuttons on a receiver to be updated, not merely the list for the currently selected programme.

In the latter half of 1988 the British Broadcasting Corporation (BBC) intends to expand its range of radiated RDS features to include the provision of a comprehensive travel service. This will enable listeners to BBC radio services with suitably equipped sets to hear all BBC travel announcements in their area, whichever BBC service they are tuned to.

The BBC RDS Travel Service aims to ensure that a listener in a given area hears all the travel announcements made concerning that area. This is achieved by diverting the listener away from the service he is currently tuned to for the duration of the announcement. The following diversions may be made by the system: I) From one national service to another.

II) From a national service to a local service.

III) From a local service to another local service.

IV) From a local service to a national service.

The travel service exploits the Other Networks feature (ON) of RDS, and uses the TA/TP flags in Group 3A/3B blocks (see Section 1,3,4, Tech Doc. 3244-E). The receiver, tuned to a BBC service will find that the TA flag for one of the Other Networks is raised. This is the cue for the receiver to tune to this other service. When it does so, the receiver will find that the TA flag has been raised on that service. The listener is now able to listen to the travel announcement. At the end of the announcement the TA flag falls and the receiver resumes reception of the original service.

The introduction of this travel service requires that every assembler fitted to a BBC VHF transmitter is informed of the traffic flag status (TA and TP) of all services that it refers to in its Other Networks (ON) information. To give examples: The assembler fitted at the Radio 2 transmitter at Wrotham must be informed of the traffic status of Radios 3 and 4, Radio London, Radio Kent, Radio Oxford, Radio Bedfordshire, Radio Sussex and BBC Essex; the assembler fitted at the Radio Oxford transmitter at Oxford must be informed of the traffic status of Radios 2, 3, and 4, and of Radio WM, Radio Bedfordshire and Radio London.

The cross-referencing of this information is the greatest problem in the implementation of a travel service, simply because the number of links between services is so very large.

It will be necessary to convey the travel information flags from the issuing studio centre to the following places: I) To all transmitters radiating that service.

II) To all transmitters making reference to that service.

At the moment, the following data distribution routes exist: I) From Broadcasting House to all main national transmitters via the NICAM PCM distribution system.

II) From all regional studio centres to Broadcasting House via the Regional Data Network.

Data routes to local radio transmitter sites from either their own studio centres, or from national services are almost non existent. The task of passing traffic flag status from local radio studio centres to national transmitters is relatively easy in comparison.

The object of the present invention is to avoid the need for land-line links by allowing the off-air reconstruction of the ON information. To this end the invention provides an RDS system wherein broadcast ON information blocks include the service number of the relevant Other Network. Moreover local radio station transmitters are equipped with a re-broadcast decoder and an assembler responsive to a data stream from the decoder to broadcast corresponding RDS messages.

The BBC RDS system uses the NICAM data path to transfer Update Format messages from the Central Computer System in London to all the main national transmitter sites. Three such routes exist, one for Radio Two, one for Radio Three, and one for Radio Four. Each packet of information leaving London is labelled with two important codes: - The destination address is a three character code identifying the assemblers on that distribution for which the data is intended. A special code exists to address all assemblers connected to the distribution.

- The service number is an eight bit code, identifying the audio service being referred to in this data packet.

An assembler will react to an Update Format message if the destination address set in the packet is either its own or the special 'global' code, and the service number is one that the assembler makes references to.

The Radio 2 NICAM distribution system carries data packets destined for all assemblers, notifying them of the contents of the Radio 2 RDS output, but it also carries data packets informing the same assemblers of the State of Radio 3 and Radio 4 for their Other Networks (ON) information.

Each BBC national service, each derivative of national services, and each local radio station has a unique service number. An assembler receivlng an Update Format message for a service number that it makes reference to, either as Its main output or In its Other Networks information, will change Its radiated output accordingly.

It is possible, by this means, to address Local Radio information used in main national transmisslons and to change It. All that must be done is to send out the relevant information as a packet, addressed to all assemblers, but with the service number of the local radio service. Every assembler that makes reference to that local radio station will, on receipt of the message, make the necessary changes.

The BBC intends to include the service number as part of the radiated RDS signal. This will be done in Group Types 3A/3B (used for ON information). The 3A/3E group has four possible variants. The service number will be radiated in block 4 of the type 2 (10) form of this group, in eight of the nine currently un-allocated bits.This block will take the form: Bit mlS - TP ( of Other Network ) Bits m1D-14 - PTY ( of Other Network ) Bit m9 - TA ( of Other Network ) Bit ma - unallocated Bits m-7 - SiN ( of Other Network ) The inclusion of the service number within this group permits a specially designed RDS re-broadcast decoder to create an Update Format data stream which gives the status of the Other Networks services referred to by the received transmission. This Update Format is then essentially the same as that which was fed into the assembler at the transmitter site.

The service number is only transmitted with ON information, never the main service. The re-broadcast decoder must be set up with the service number of the station it is tuned to loaded into its memory. The decoder is then able to produce an Update Format stream relating the following information to a connected assembler:: - Main Service SN Service Number Pi Programme identification PS Programme Service Name PTY Programme Type PIN Programme Identification Number MS Music/Speech Dl Decoder information TA Traffic Announcement TP Traffic Programme RT Radlotext - Other Networks SN Service Number Pl Programme IdentIfIcatIon PTY Programme Type PIN Programme IdentIfication Number TA Traffic Announcement TP' Traffic Programme An example will illustrate how this may be used for travel purposes: A national site radlates Radio 2. This carries RDS Information about Itself, but also about Radio Kent and Radio London through the Other Networks (ON) information.

The Central Computer System generates an Update Format Message informing all transmitters that Radio Kent is making a traffic announcement (TA flag on). The Radio 2 transmitter broadcasts this through the ON facility. The local radio station transmitter at Radio Kent Is equipped with a re-broadcast receiver tuned to the nearest Radio 2 transmitter. The re-broadcast decoder (CS/23) produces a stream of data informing the assembler that Service Number 32 (Radio Kent) has raised the TA flag. This, of course, relates to this transmitters main service. As a result, the TA flag of the Radio Kent RDS service is raised. The flag is cleared at the end of the announcement by the same mechanism.

All transmitters in the area which make any reference to Radio Kent will receive the same Update Format message from their rebroadcast decoders, and the message will cause the TA flag for Radio Kent to be raised in their outputs.

The Central Computer System is the controlling element for all traffic flag changes. It initiates all Update Format messages.

Those messages supplled to assemblers at remote transmitters are merely re-created forms from off-air reception of main transitters. Through this mechanism the computer has the ability to alter the PI, PS, PTY, PIN, TA and TP outputs of all local services throughout the country.

Therefore, a local radio station wishing to make a travel announcement must communicate this fact with the computer.

The communication path from studio centres to the Central Computer will be the Regional Data Llnk. Spare bits will be used within this channel to inform the computer of a local radio statlon's change In travel flag status. The change In status wlll be acknowledged by the central computer uslng the Data Link.

Examples of Travel Announcements Some examples of the use of the travel facIlIty are given here to Illustrate the flexibIlIty that this approach offers: A Local Radio Statlon To Initiate a travel announcement, the studio centre sends a packet to the Central Computer using the Regional Data Link. The computer acknowledges this using the data llnk and proceeds to generate an Update Format message to Inform all assemblers of the change In the traffic status for this particular local radio service. This message Is sent via the NICAM links for Radio 2, Radlo 3 and Radio 4. Wherever the particular local radio station is listed In the ON Informatlon of national assemblers the assembler takes act ion and sets the TA flag for that ON service.This happens on Radio 2, Radio 3 and Radlo 4.

All local radio transmitters in the coverage area of the main transmitter are fitted with re-broadcast recelvers and decoders. These will normally be tuned to the Radio 2 service (since this Is on the air 24 hours a day). These local radio transmitter sites will then recreate an Update Format feed that Includes the reference to the traffic flag changing on this particular service.

If the transmitter site makes reference to the originating service via its ON Information, or if indeed it radiates that service itself, the status of the relevant traffic flag will change.

Thus, whether a listener is tuned to the announcing station, to a neighbouring BBC local station, or to any national BBC service, he will be able to hear the travel announcement.

Radio 2 It may well be that an announcement needs to be made which affects a very large portlon of the populatlon (eg M1 closed). Radio 2 may decide to announce this nationally. Radio 2 will Inform the central computer of the change in their travel status. This will Initiate Update Format messages via the Radio 2, Radio 3 and Radio 4 NICAM paths. All national assemblers will be Informed by this route. Radio 2 transmitters will be radiating the TA flag on their main service, Radio 3 and 4 transmitters as an Other Networks reference.

BBC local radlo transmitter sites will re-create an Update Format data stream using their decoders tunea to Radio 2. The Update Format stream will contaln references to service 221 (Radlo 2).

because this number will have been set on the decoder when It was tuned to Radio 2. This update stream, when fed to an assembler at the local radlo site, will then set the Other Networks TA flag for Radio 2.

The effect of this actlon will be noticed by all listeners to BBC radio who have an RDS receiver In the traffic announcement mode.

These listeners will all hear the Radio 2 traffic announcement, whatever BBC service they were Initially tuned to, throughout the entIre UK.

Radio 4 This situation Is similar to that of Radio 2 making such an announcement. It Is worth Including as an example Just to Illustrate that national announcements are not limited to Radio 2, even though Radio 2 will be used as the update path to local radio transmitter sites.

The Radio 4 announcer initiates a travel announcement in the same way as his colleagues in Local radio and Radio 2, by communicating with the Central Computer System. The Computer sends Update Format message to all Radio 2, 3 and 4 assemblers. The Radio 4 assemblers set their main TA flag, the Radio 2 and 3 assemblers set their ON TA flag for Radio 4.

The decoders fitted at all local radio transmitter sites, and tuned to Radio 2, produce a stream of Update Format data which includes the TA flag set for service 240 (Radio 8).

Although Radio 4 is a national service, there are parts of the UK where it cannot be received. In these areas the assemblers will not have service 240 listed in their ON (Other Networks) services. The Update Format messages relating to this service produced by their decoders will be ignored. Only transmitter sites making reference to this service will make the change in the TA flag status for Radio 4.

Thus, in the case of Radio 4, only those listeners to BBC Radio within the coverage area of a Radio 4 transmitter will make any diversion from their tuned service.

Radio Scotland If a Radio Scotland presenter wishes to make a travel announcement the same mechanism applles again. The message travels to London via the Regional Data Llnk, and from the Central Computer to all main transmitters in the UK. All transmitters in Scotland, and those In the very north of England that refer to Radio Scotland, will change the status of the respective TA flag In their output. In this case only listeners in the Radio Scotland coverage area will be diverted to hear the announcement.

An Important part of the travel service must be the phasing of travel announcements from varlous sources. For example a Radlo 2 announcer would wish to walt for a local radio announcer to complete his announcement before holding the entIre UK lIstenIng populatlon for his own announcement.

In London, the monitoring Is falrly easy to perform, because the Central Comeuter knows the traffic status of every local radio station In the country. A simple program running on this machine can drive a lamp circuit indicating that a traffic announcement is being made somewhere. The announcer can wait for this lamp to extinguish before initiating his own travel announcement.

Local radio studio centres will need to be equipped with their own decoders tuned to their local Radio 2 transmitter. The Update Format data that this decoder produces may then feed one or more Intelligent display panels indicating the traffic status of all services In theIr cover ace area, Including their own. This will ensure that their announcements do not collide with adjacent BBC local radio services, or with national travel announcements, and gives them the ultimate feedback to show that listeners are in fact diverted to their own service.

When making an announcement it has been assumed that the TA flag is switched a few moments before the announcement is goIng to be made. The feedback system outlined above will work much better if It were possible to indicate that an announcement Is aoino to be made soon, essentially reserving the traffic announcement facility. The TP flag could be used for this purpose. The local radio announcer who wishes to give a travel flash checks to see that no one else In his area has reserved the Traffic Announcement facility (ie their TP on ). If not, then he switches his own TP flag on, reserving the traffic facility for himself. At the end of his record or item, when he Is ready to make such an announcement, he turns the TA flag on by some actlon (button or Jingle). At the end of the announcement he turns off both the TA and the TP flags, freeing the system for some other person to use.

Claims (4)

CLAIMS:

1. A radio data system in which a radio transmitter broadcasting a first service identified by its service number transmits digital codes in addition to programme material, the codes providing information about the first service and including Other Network codes which provide information about other networks, characterized in that the other network codes further include the service numbers of the Other Networks to which they respectively pertain.

2. A radio station comprising a transmitter which broadcasts a first service identified by its service number and transmits digital codes in addition to programme material, the codes providing information about the first service and including Other Network codes which provide information about other networks, a decoder responsive to received codes addressed to the station or to the station as a member of a group, and means responsive to received Other Network codes which include the service number of the first service to update its transmitted digital codes in accordance with the information in the received codes.

3. A radio station according to claim 2, further comprising an assembler responsive to received Other Network codes which include the service number of a service not broadcast by the station to assemble and transmit Other Network codes which relay the received codes, including the service numbers.

4. A radio station according to claim 3, wherein the assembler is responsive only to received Other Network codes which include specified service numbers.