Siemens TC12 Installation, Commissioning And Maintenance Handbook page 200

The learning of the second state is automatic once the controller has been
switched to that state and requires no manual intervention.
This means that it is not strictly necessary to manually switch the controller into the
other state as the second learning sequence will be invoked automatically at the
first dim/bright change, after the initial learning sequence was invoked.
It should be noted however, that lamp failures cannot be detected when the
controller is in a particular state (dim or bright) unless the characteristics of the
junction have been learnt in that state. If the learning of the second state is left to
occur automatically at the next dim/bright change and the lamp failure occurs
during or just after the change, it will not be detected by the LMU until the
controller reverts back to the original state in which the junction learning was
invoked.
6.4.4.3 Checking that Lamp Failures are Detected
The installation engineer may check that lamp failures are indicated when they
occur and that lamp replacements remove the fault indication.
These checks should be carried out after the junction characteristics have been
learnt.
Remove any lamp and wait for the LMU to find the failure. Indication that the lamp
failure has been found will be given by the lighting of the system fail LED on the
Controller Main Processor PCB, and by the appropriate entry in the fault log.
Further lamps may be removed to check that lamp failures can be detected on
other controller outputs.
666/HE/43100/000
TC12 Installation, Commissioning & Maintenance Handbook
Page 190 Issue 10