When U.S and NATO allies or Coalition partners work together on a combined operation, they need to use radio communications to co-ordinate their efforts. However, each nation (U.S., NATO or Coalition) often utilize different encryption schemes or keys in their radios, creating a communications gap between their systems.
Read about how the ICRI solves this problem: https://www.c-at.com/blog/how-to-connect-radios-with-different-types-of-encryption-comsec