That refers to the Beidou PRM module: The PRM module is a precision ranging code generator, and provides the function of decoding Q messages.
Support BD2-B1\/B3, GPS-L1 frequency points, can achieve BD2 system single frequency\/dual frequency\/multi-frequency positioning, GPS single frequency positioning, multi-system combination positioning and high-precision fast orientation. With BD2 system military code module (PRM, encryption and decryption chip), support BD2 system military code capture, tracking, message decryption processing functions, is a high performance military grade user equipment.