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RDS features

1.1 Alternative Frequencies list (AFs)

The list(s) of Alternative Frequencies give(s) information on the various transmitters broadcasting the same programme in the same or adjacent reception areas, and enable receivers equipped with a memory to store the list(s), to reduce the time for switching to another transmitter. This facility is particularly useful in the case of car and portable radios.

1.2 Clock Time and date (CT)

Time and date codes use Coordinated Universal Time (UTC) and Modified Julian Day (MJD). If MJD = 0, the receiver shall not be updated. The listener, however, will not use this information directly and the conversion to local time and date will be made in the receiver's circuitry. CT is also used as time stamp by various RDS applications and thus it shall be accurate.

1.3 Dynamic PTY Indicator (PTYI) using DI

This flag is one of four DI flag options. It indicates if PTY codes are switched dynamically.

1.4 Extended Country Code (ECC)

RDS uses its own country codes, composed of a combination of a Country Identifier CI and an Extended Country Code ECC. The first most significant bits of the PI code carry the RDS Country Identifier. The four-bit coding structure only permits the definition of 15 different codes, 0x1 to 0xF. Since there are many more countries to be identified, some countries have to share the same CI code which does not permit unique identification. Hence, there is the need to use the Extended Country Code which is transmitted in Variant 0 of Block 3 in type 1A groups and only both codes together, the Country Identifier CI in bit b15 to b12 of the PI code and the ECC transmitted in group 1A render a unique combination. The ECC is an 8 bit code.

1.5 Enhanced Other Networks information (EON)

This feature can be used to update the information stored in a receiver about programme services other than the one being received. Alternative Frequencies, the PS name, Traffic Programme and Traffic Announcement identification as well as Programme Type can be transmitted for each other service. The relation to the corresponding programme is established by means of the relevant Programme Identification code.

1.6 Linkage information

Linkage information provides the means by which several programme services, each characterised by its own PI code, may be treated by a receiver as a single service during times when a common programme is carried. Linkage information also provides a mechanism to signal an extended set of related services.

1.7 Open Data Applications (ODAs)

Open Data Applications are a very effective and flexible way for adding additional applications to an RDS service. A number of different ODAs may exist on any service, subject to capacity. ODAs may be transmitted constantly, or only when required (e.g. an application which provides an alert in case of extreme weather conditions, etc.). The Open Data Applications are conveyed in a number of allocated groups in an RDS transmission in stream-0 or on any of the upper streams. The allocated groups are indicated by the use of the type 3A group which is used to identify to a receiver the data application in use in accordance with the registration details in the open data applications directory. Identification of the ODAs in the upper streams is accomplished by header functions 10000000 through 10000011, where channel numbers are linked to AID numbers in a similar way as with the 3A method.

1.8 Programme Identification (PI)

The Programme Identification (PI) is a code enabling the receiver to distinguish between audio programme content. The most important application of the PI code is to enable the receiver in the event of bad reception, to switch automatically from the frequency used at that time to an alternative frequency. The criterion for the change-over to the new frequency would be the presence of a better signal having the same Programme Identification code. It follows therefore that the PI shall be allocated in such a way that it uniquely distinguishes each audio programme content from all others in the same area.

The actual values of the PI code have no direct use for the end consumer as it is not intended for direct display. Of importance, however, is that a methodology exists within a broadcast area (i.e. any given country), to ensure uniqueness of PI code allocations to programme services.

In Europe, for example, a pool of theoretical 65 536 unique values have been allocated firstly at international level, and thereafter at national and regional levels for allocation by the appropriate national authorities. Hence, there is a structure to PI code allocations widely used in Europe.

The primary purpose of the PI code is to facilitate automatic tuning between different transmitters all carrying the same audio content. Or in case of a regional programme structure automatic tuning can be done to PI codes with a generic relationship differing in the 2nd nibble the physical location of the transmitter itself is immaterial in determining the PI code. It is the location of the origin of the audio programme which determines the value of the PI code to be used. Hence, transmitters broadcasting an international programme originating in one country and being relayed by transmitters in other countries would carry the same PI code, regardless of their locations, or otherwise automatic tuning between transmitters cannot occur. Additionally, as the relay transmitter will relay the RDS data, as well as the audio content, it is obvious that the PI code allocated to the transmitter at the head of the chain of transmitters will simply be re-broadcast by all transmitters in the relay chain.

As the PI code has a unique value in each area, it may be thought of as a primary key to which all other RDS parameters about a particular service are referenced. For this reason, the PI code appears in every RDS group type on data-stream 0, and it is the PI code which is used when referring to other programme services, as in EON.

Short-range transmitting devices connected to audio sources, when using RDS features, also require the use of a specific PI code.

1.9 Programme Service name – (PS)

This is the label of the programme service consisting of eight alphanumeric characters coded with the basic RDS character set, which is displayed by RDS receivers in order to inform the listener what programme service is being received from the station to which the receiver is tuned. An example for a name is ‘Radio 21’. The programme service name is not intended to be used for automatic search tuning and shall not be used for giving sequential information.

If a broadcaster wishes to transmit the long Programme Service name, group 15A shall be used in addition.

The Programme Service name comprises eight characters, intended for STATIC display on a receiver. It is the primary aid to listeners in programme service identification and selection. The use of PS to transmit text other than a single eight character name is not permitted as it disables the intended functionality, specifically for car radios. PS shall not be used for programme-related information: RT or eRT shall be used instead. Receivers shall not use the same display area for the PS name and RT/eRT. These display areas shall whenever possible be separated in a receiver.

1.10 Programme Service name – (Long PS or LPS)

The Long PS, using the 15A group, is an alternative to the PS. It allows use of more than eight characters (up to 32 bytes for the string of characters). As UTF-8 coding is supported, the range of languages covered is increased. For backwards compatibility with existing RDS receivers the PS shall also be transmitted, using the 0A group. The use of the Long PS to transmit text other than a Programme Service name is not permitted. RT or eRT shall be used for this purpose. The Long PS is complementary information to the PS and it may be used to replace the PS on a display. While the acquisition of the PS is time critical, the acquisition of the Long PS is not.

1.11 Programme Type (PTY)

This is an identification number to be transmitted with each programme item and which is intended to specify the current Programme Type within 32 possibilities (see IEC 62106-4). This code could be used for search tuning. The code will, moreover, enable suitable receivers and recorders to be pre-set to respond only to programme items of the desired type. The last number, i.e. 31, is the alarm identification which is intended to switch on the audio signal when a receiver is operated in a non- reception mode.

1.12 Programme Type Name (PTYN)

The PTYN feature is used to further describe current PTY. PTYN permits the display of a more specific PTY description that the broadcaster can freely decide (e.g. PTY = 4: Sport and PTYN: Football). The PTYN is not intended to change the default eight characters of PTY which will be used during search or wait modes, but only to show in detail the programme type once tuned to a programme. If the broadcaster is satisfied with a default PTY name, it is not necessary to use additional data capacity for PTYN. The programme type name is not intended to be used for automatic PTY selection and shall not be used for giving sequential information.

1.13 RadioText (RT)

These are text transmissions with 64 characters at maximum, coded by using the basic RDS character set, addressed to receivers, which would be equipped with suitable display facilities. If a display which has fewer than 64 characters is used to display the RadioText message, then memory shall be provided in the receiver/decoder so that elements of the message can be displayed sequentially. This may, for example, be done by displaying elements of text one at a time in sequence, or, alternatively by scrolling the displayed characters of the message from right to left

1.14 enhanced RadioText (eRT)

This is an ODA and an alternative to RadioText to enable text transmissions with 128 bytes at maximum, coded in UTF-8 and addressed to receivers, which would be equipped with suitable display facilities. As eRT is an ODA, it is thus compatible with receivers not using this feature. This feature supports a wider range of languages than RT.

1.15 RadioText Plus (RT+ and eRT+)

This feature allows tagging specific elements of RadioText (RT and eRT) and permits, among many other possibilities, to improve the presentation on a display for both. The tagged RadioText elements can also be stored as a list that could be searched by the end user. A popular application is to list music titles and artist names. There exist now two ODAs, one for RT and another one for eRT. Both ODAs are compatible with receivers not using this feature.

1.16 Traffic Announcement identification (TA)

This is an on/off switching signal to indicate when a Traffic Announcement is on air.

The signal can be used in receivers to

a) Switch automatically from any audio mode to the Traffic Announcement,

b) Switch on the Traffic Announcement automatically when the receiver is in a waiting reception mode and the audio signal is muted,

c) Switch from a programme to another one carrying a Traffic Announcement, as signalled by EON.

After the end of the Traffic Announcement the initial operating mode shall be restored.

1.17 Traffic Message Channel (TMC)

This feature is intended to be used for the coded transmission of traffic information (ALERT-C protocol). The coding for TMC is separately specified in the IS0 14819 series. It is a set of ODAs, open or encrypted for conditional access. As TMC is an ODA it is thus compatible with receivers not using this feature.

1.18 Traffic Programme identification (TP)

This flag indicates that the tuned programme carries traffic announcements. The TP flag shall only be set on programmes which dynamically switch on the TA identification during Traffic Announcements. The signal shall be taken into account during automatic search tuning.