﻿The behaviour parameterised at this point is executed in the event of a bus or mains voltage failure (mains voltage of the gateway). If there is a voltage failure on the DALI cable (e.g. due to short-circuit, cable break, mains voltage failure on gateway), then the assigned DALI operating devices will also show the configured behaviour in the event of a bus voltage failure. This is guaranteed because the parameter setting in the DALI operating devices is applied as the "System Failure Level" for the brightness after an ETS programming operation.

*Brightness value*: The DALI operating devices are set to the value specified by the "Brightness value" parameter via the DALI line in the event of a bus voltage failure at the gateway, provided the mains voltage supply of the gateway is still switched on. If the mains voltage fails at the gateway, this command can no longer be issued. In this case, the DALI operating devices set themselves to the programmed system failure level corresponding to this parameter, provided their mains voltage supply is still switched on.

*Switch off*: The DALI operating devices are switched off via the DALI cable in the case of a bus voltage failure if the mains voltage supply of the gateway is still switched on. If the mains voltage fails at the gateway, this command can no longer be issued. Here, too, the DALI operating devices set themselves to the programmed system failure level that corresponds to this parameter, provided their mains voltage supply is still switched on.

*No reaction*: The gateway does not send any commands to the DALI operating devices in the event of a bus or mains voltage failure. The assigned DALI operating devices, provided their mains voltage supply is still switched on, show no response and remain in the brightness state that was last set.
