RDS Germany - TMCpro: Multi-group messages

RDS Germany - TMCpro: Multi-group messages

What is a Multi-group message and what is special for RDS Germany - TMCpro?

In most of countries, RDS-TMC messages are sent entirely in a single RDS group (Single-Group Message – SGM). However, a proportion (especially in Germany for TMCpro) uses two or more groups (Multi-Group Messages – MGM). This may be the case when a message cannot be transmitted using a single 37-bit Group, and more than one TMC group is needed.

Multi-Group messages are sequences of between two and five type 8A groups, which constitute a detailed RDS-TMC message. This means, up to a total of five groups may be used to describe a particular event.

Therefore, handling MGM in a receiver requires extra care and rules, for example:

Information in the 2nd group modifies the information in the 1st group. This can happen with
+ Control Codes (Label 1) – because these can change direction of the described event, increase extent, change importance of the message
+ Quantifiers (Labels 4 and 5) - the message is incomplete without a quantifier

Each part of a Multi-Group message must be received and used in the correct order