Indicators are the first of the 4 kinds of data exchanged
Indicators are defined as (identifier, value). Identifier is an integer, value can be 1, 2 or more bytes according to the indicator definition stored on the server database
Indicators are automatically stored in the database with a timestamp
Indicators flow is mainly from microcontroller to server but eventually from the server to the microcontroller
Indicators are data relative to the stations
Typically an indicator is a microcontroller parameter that has to be stored in database and can be updated from the server