After start-up has been successfully completed, cyclic self-monitoring tests will be run during operation. In the event of a positive test result, a specified monitoring signal will be issued and stored in a non-volatile(NV) memory – the monitoring signal memory – along with the assigned date and time (see Chapter “Monitoring Signal Recording (Function Group MT_RC)”).

The self-monitoring function monitors the built-in battery for any drop below the minimum acceptable voltage level. If the associated monitoring signal is displayed, then the power supply module should be replaced within a month, since otherwise there is the danger of data loss if the supply voltage should fail. Chapter “Maintenance Procedures in the Power Supply Area” gives further information on maintenance procedures.