The MD1701S test block cooperates with the CJ28TS test module to provide safe, flexible and reliable access to the power system protection or measurement circuit for monitoring, verification and secondary test. The CJ28TS test module can be inserted into the MD1701S test block, and they can be fixed together with two screws. The MD1701S test block provides 7 subtypes to meet different requirements, as shown in the following figure. For example: “MD1701S-4I6U” means that there are 4 current channels and 6 voltage channels.