Radio Data System is a communication protocol that allows to send small amounts of digital information in a common FM radio broadcast. Aside from time and date, this commonly is the name of the station, or information about the program that is currently broadcast. First tests were done in 1983 and 1984, the standard was officially introduced in 1988.
The following types of information can be sent:
- Programme Service name, usually the station name. There's a short version (with 8 alphanumeric characters), and a long version (16 characters, UTF-8)
- Programme type: One of 16 possible types, for example news, or pop
- PTY-31 allows to switch to a mode for emergency messages. Newer receivers often disregard this; as it was never used correctly
- Traffic Programme: If enabled, the station also carries messages about read traffic
- Traffic Announcement: Traffic announcements are flagged
- Enhanced Other Networks: If this channel doesn't offer traffic info, it is possible to switch to another channel for traffic information
- Traffic Message Channel: Coded messages about traffic, to be displayed in a GPS or navigation device
- Alternative Frequency: Broadcast another frequency for the current programme
It is possible to transmit Radio Text. In theory, it is possible to transmit 64 characters per line.