A modular safety system for safety control in emergency stop applications includes a base module and at least one extension module, wherein each module is arranged in a housing with a rail-mounting base, so that the modules are located in a side-by-side arrangement when mounted to the rail. The modular safety system also includes means for setting of required input and output functions, wherein the setting means is located in a side wall of the module housing, so that after mounting the modules to the rail, the setting means is covered by an adjacent module.