2023-01-31 note: 
This version（DZ_K21B1_ML_STD_V4.51.410_230114.zip）  supports IP-Speaker、FM2466、Solar camera(but need to been noted only 64 channel M series NVR don't support Solar camera.)

2023-4-11 note：
（1）、This version（DZ_K21B1_ML_STD_V4.51.410_230114.zip） is the latest customized firmware of M series NVR, it supports IP-Speaker、FM2466、Solar camera
（2）、Default language is Italian
（3）、The password must contain at least three of the four types of uppercase, lowercase, numbers and special characters