Other early pioneers employed rotating mirrors, or vibrating mirrors known as mirror galvanometers. The Grassot Fluxmeter solves a particular problem encountered with regular galvanometers. Almost all of these galvanometers are of the moving magnet type. The mask is conjugate to x and z galvanometers. These galvanometers were bulky and delicate. These were called "tangent" galvanometers and had to be oriented before use. The prosecutor withdraws the case as the galvanometers are now repaired. The galvanometer is constructed as a number of moving-iron galvanometers, sharing the same excitation coil. The receiving instrument consisted of six galvanometers with magnetic needles, suspended from silk threads. The faster the galvanometers, the smoother and more flicker-free the projected image. In his studies of electricity, he designed sine and tangent galvanometers. A major early use for galvanometers was for finding faults in telecommunications cables. Because of this phenomenon, astatic needles were often used in galvanometers. Sensitive galvanometers have been essential for the development of science and technology in many fields. Galvanometers come in two main groups&colon; "open loop" and "closed loop".