From the DS10A manual.
Replacing batteries
Open the battery compartment and replace the batteries with two
AA alkaline batteries. After replacing the batteries, the following
steps are necessary to determine that the Console still recognizes
the DS10A.
• Place the Console’s slide switch to RUN2.
• Press TEST on the DS10A. If the Console chimes, it recognizes
the DS10A and no further action is necessary.
If the Console did not chime:
Place the Console’s slide switch to INSTALL. Press TEST on the
DS10A. The Console beeps and logs in the DS10A to the next
available zone. To make sure the Console logs the DS10A back
into the same zone it was allocated to before you changed the
batteries, wait four hours after removing the old batteries before
reinstalling (until the appropriate zone indicator on the Console
starts flashing).
Looks like if you wait until the zone indicator starts flashing then put the batteries into the new DS10A and press the test button it will end up in the correct Zone without redoing the whole thing.
Bob