A downhole system includes a controller located at the surface, a gun string located in a wellbore, the gun string including plural gun assemblies, a thru-line connecting the controller to the gun string, and a detonator block attached to a given gun assembly. The detonator block includes an addressable switch assembly. The gun assembly includes an end plate mechanism that electrically connects to the detonator block. The detonator block has at least one spring-loaded contact connected to the thru-line and the end plate mechanism includes a round electrical contact made as a printed circuit board, and the spring-loaded contact touches the printed circuit board.