Complex sentence: Tens of thousands of these units were distributed to US state civil defense agencies and even though large numbers have been sold off as surplus to civilian users, many remain in use with first responders and state emergency management agencies today.
Split into simpler sentences: Tens of thousands of these units were distributed to US state civil defense agencies. Even though large numbers have been sold off as surplus to civilian users, many remain in use with first responders and state emergency management agencies today.