Sharpening stones

Apparatus for recording, transmission or reproduction of sound and images, in particular, fiber optic components for optical data transmission and for telecommunications and data communications; namely receivers, transceivers, transponders, amplifiers, multiplexers and demultiplexers, telecommunication switches and optical filters; ASE (Amplified Spontaneous Emission) sources, broadband sources, namely testers and fiber optic instruments for fiber optical data transmission, for telecommunicat...