While M12 connections could not previously be tested for the most common installation errors, there is now a suitable M12-X and -D coded extension set for this area of application for the Kapri plus test device from Metz Connect and similar and compatible installation testers available on the market. The installation tester can be used for new installations, retrofitting and repairs of mainly field-terminated connectors or installation cables. By testing the installation cable directly after installation, cost-intensive failures, troubleshooting during commissioning and reworking can be shortened or avoided in advance. Applications for the M12 extension set can be found in all areas of structured building cabling, especially industrial cabling (Industrial Ethernet) with M12 components, communication cable systems, automation/control systems, industrial automation, building automation or traffic automation.