Measuring instruments; testing apparatus and instruments for cables, cable installations or for piping; electric surge generators; difference probe coils (electric); electric channel filters; cable defect detectors; capacitors; dischargers being parts of measuring instruments; sound-frequency generators; emitters and receivers, all for cable detectors; testing instruments for underground mining purposes; flow meters, transducers, electric measuring and electric recording instruments, electric current supply units included in Class 9 and gas leak indicators, all being for use in environmental protection; water leak indicators; slide valve cap and rod detectors; apparatus for detecting metallic or plastic lines; leak indicators for the detection of pipe fractures; apparatus and instruments, all for detecting cables, cable installations or water conduits; apparatus and instruments, all for detecting leaks in distance heating installations; electronic apparatus for analysing water leaks and for the construction and reconstruction of plans;