The AD Series Desktop Power Supplies include a battery back up output as standard. This can be connected to maintain charge in a lead acid battery to supply power in the event of a mains failure.
As a neat alternative to a loose battery, Alfatronix also supply a battery back up box, P/N AD BBB. This is designed to fit underneath the desktop supply and radio assembly and includes a 7Ah lead acid gel battery, presenting all three components as one tidy desktop assembly.The battery back up box also includes a speaker (mounted on the front of the unit) which can be connected to the radio if needed.