Profile: Terahertz Technologies, Inc. specializes in offering fiber optic test equipment, radiometric, industrial and conversion equipment. The C-995 phase-locked-loop optical chopper incorporates direct digital synthesis in order to provide rock-solid, crystal controlled accuracy and stability. Its chopping frequency can be controlled to a precision of 0.001 Hz, and has effectively zero frequency drift. It features a five digit LED display that indicates the internally set chopping frequency, or in the external sync mode, the measured frequency of the external clock signal. The LT-880 fiber optic laser tachometer is a non-contact instrument designed to measure rates of rotation, by sensing the presence or absence of a reflective surface in its optical beam. These are typically provided by affixing an easily made black and white encoder to the surface of the rotating component.