The original SMX-6 and AMB-5 units came with an internal battery for memory backup. These older units need to have a Backup Retro Module installed. This involves the removal of the battery and the replacement of the processor with the retro module that has a firmware update and EEprom memory backup. The part can be odered from the Crown Parts Department.
The SMX-6 Backup module is part number 125505-1.
The AMB-5 Backup module is part number 125506-1.