RDS features are usually referred to by short abbreviations. This glossary migrates the full legacy feature guide into the new site layout.
RDS features
1.1 Alternative Frequencies list (AFs)
The list or lists of Alternative Frequencies give information on the various transmitters broadcasting the same audio programme in the same or adjacent reception areas. They enable receivers to store the lists and reduce the time needed to switch to another transmitter. This facility is particularly useful in 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). The listener does not use this information directly; conversion to local time and date is made in the receiver circuitry. CT is also used as a timestamp by various RDS applications and therefore has to be accurate.
1.3 Dynamic PTY Indicator (PTYI) using DI
This flag is one of four DI flag options. It indicates whether PTY codes are switched dynamically.
1.4 Extended Country Code (ECC)
RDS uses its own country codes, composed of a Country Identifier (CI) and an Extended Country Code (ECC). The most significant bits of the PI code carry the RDS Country Identifier. The four-bit coding structure only permits 15 different codes, 0x1 to 0xF. Since many more countries have to be identified, countries must share CI codes, which does not permit unique identification.
The Extended Country Code is therefore transmitted in type 1A groups. Only the combination of the Country Identifier in bits b15 to b12 of the PI code and the ECC transmitted in group 1A makes a unique country combination possible. The ECC is an 8-bit code.
1.5 Enhanced Other Networks information (EON)
This feature can update 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, and Programme Type can be transmitted for each other service. The relation to the corresponding programme is established by 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 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 an effective and flexible way to add applications to an RDS service while remaining backwards compatible. A number of ODAs may exist on any service, subject to capacity. ODAs may be transmitted constantly, or only when required, for example for an alert application in extreme weather conditions.
Open Data Applications are conveyed in allocated groups in an RDS transmission in stream 0, or on any of the three upper streams. The allocated groups, or the respective data channels in RDS2, are indicated by Application Identification (AID) signalling.
1.8 Programme Identification (PI)
Programme Identification is a code that enables the receiver to distinguish between audio programme content. Its most important application is to let the receiver switch automatically from the frequency currently used to an alternative frequency when reception is poor. The criterion for changing to the new frequency is the presence of a better signal with the same PI code.
The PI code must therefore be allocated so that it uniquely distinguishes each audio programme content from all others in the same area. The actual PI code values have no direct use for the listener and are not intended for direct display. What matters is that a methodology exists within a broadcast area, such as a country, to ensure unique PI code allocation to programme services.
In Europe, for example, a pool of 65,536 theoretical unique values has been allocated first at international level and then at national and regional levels for allocation by the appropriate authorities. This gives PI code allocation a structure that is widely used in Europe.
The primary purpose of the PI code is automatic tuning between different transmitters carrying the same audio content. In a regional programme structure, automatic tuning can also be done to PI codes with a generic relationship that differ in the second nibble. The physical location of the transmitter is immaterial in determining the PI code. The location of the origin of the audio programme determines the PI code to be used.
Transmitters broadcasting an international programme originating in one country and relayed by transmitters in other countries would carry the same PI code regardless of their locations, otherwise automatic tuning between transmitters cannot occur. Since relay transmitters relay the RDS data as well as the audio content, the PI code allocated to the head of the transmitter chain is re-broadcast by all transmitters in the relay chain.
Because 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 service are referenced. For this reason, the PI code appears in every RDS group type on data-stream 0 and is also used when referring to other programme services, as in EON.
Short-range transmitting devices connected to audio sources also require a specific PI code when using RDS features.
1.9 Programme Service name (PS)
The Programme Service name is the label of the programme service. It consists of eight alphanumeric characters coded with the basic RDS character set and is displayed by RDS receivers to inform the listener which programme service is being received. An example is Radio 21.
The programme service name is not intended to be used for automatic search tuning and must not be used for sequential information. If a broadcaster wishes to transmit the Long Programme Service name, group 15A must be used in addition.
The Programme Service name is 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 because it disables the intended functionality, especially for car radios. PS must not be used for programme-related information; RT or eRT should be used instead. Receivers should not use the same display area for PS and RT/eRT whenever separate areas are possible.
1.10 Programme Service name (Long PS or LPS)
The Long PS, using the 15A group, is an alternative to PS. It allows more than eight characters, up to 32 bytes for the string. Since UTF-8 coding is supported, the range of covered languages is increased. For backwards compatibility with existing RDS receivers, the short PS must also be transmitted using the 0A group.
The use of Long PS to transmit text other than a Programme Service name is not permitted. RT or eRT must be used for that purpose. Long PS is complementary information to PS and may be used to replace PS on a display. While acquisition of PS is time critical, acquisition of Long PS is not.
1.11 Programme Type (PTY)
Programme Type is an identification number transmitted with each programme item to specify the current programme type within 32 possibilities. IEC 62106-4 contains an annex with translations into many languages in addition to English. PTY can be used for search tuning and can allow suitable receivers and recorders to respond only to programme items of the desired type. The last number, 31, is the alarm identification intended to switch on the audio signal when a receiver is operated in a non-reception mode.
1.12 Programme Type Name (PTYN)
PTYN further describes the current PTY. It permits display of a more specific PTY description freely chosen by the broadcaster, for example PTY = 4: Sport and PTYN: Football.
PTYN is not intended to change the default eight characters of PTY used during search or wait modes, but only to show programme type detail once tuned to a programme. If the broadcaster is satisfied with the default PTY name, no additional data capacity need be used. PTYN is not intended for automatic PTY selection and must not be used for sequential information.
1.13 RadioText (RT)
RadioText consists of text transmissions with a maximum of 64 characters, coded with the basic RDS character set and addressed to receivers with suitable display facilities. If a display has fewer than 64 characters, the receiver or decoder should provide memory so that elements of the message can be displayed sequentially, for example one text element at a time or by scrolling the message from right to left.
1.14 enhanced RadioText (eRT)
Enhanced RadioText is an ODA and an alternative to RadioText. It enables text transmissions with a maximum of 128 bytes, coded in UTF-8, and addressed to receivers with suitable display facilities. Because eRT is an ODA, it is compatible with receivers that do not use the feature. It supports a wider range of languages than RT.
1.15 RadioText Plus (RT+ and eRT+)
RadioText Plus allows specific elements of RadioText, RT and eRT, to be tagged. Among many other possibilities, this can improve presentation on a display. Tagged RadioText elements can also be stored as a list that the end user can search. A popular application is listing music titles and artist names. There are now two ODAs, one for RT and another for eRT. Both are compatible with receivers that do not use the feature.
1.16 Traffic Announcement identification (TA)
TA is an on/off switching signal indicating when a Traffic Announcement is on air. The signal can be used by receivers to switch automatically from any audio mode to the Traffic Announcement, switch on a Traffic Announcement when the receiver is in a waiting reception mode and audio is muted, or switch from one programme to another carrying a Traffic Announcement as signalled by EON. After the Traffic Announcement ends, the initial operating mode should be restored.
1.17 Traffic Message Channel (TMC)
TMC is intended for coded transmission of traffic information using the ALERT-C protocol. TMC coding is separately specified in the ISO 14819 series. It is a set of ODAs, open or encrypted for conditional access. Since TMC is an ODA, it is compatible with receivers that do not use the feature.
1.18 Traffic Programme identification (TP)
This flag indicates that the tuned programme carries traffic announcements. The TP flag should only be set on programmes that dynamically switch on TA identification during Traffic Announcements. The signal is taken into account during automatic search tuning.