Is the performance correct? Is the device still in working order, or is there perhaps a safety risk? Are the relevant limit values being complied with? Test equipment and test devices deliver fast and concrete answers to these questions and more. This saves money and protects objects from damage and people from sustaining injury. Voltage and continuity testers display closed circuits, whereas photovoltaic measuring devices monitor the performance of the solar panels. VDE testing devices and installation testers are relied upon. They are used to maintain and observe prescribed limit values, for example. Lamp testers facilitate the inspection of illuminants and reduce maintenance times considerably. Cable and network testers can reliably detect connection errors.