The C995 Optical Chopper is equipped with a bi-directional RS-232 port that permits the user to set the desired chopping rate to a resolution of .001 Hz and to read the status of the instrument. 

The C995 is designed with a phase-locked-loop control system, allows the chopping rate to also be synchronized to a user-supplied external clock ranging from 4 Hz to 5 KHz. The controller is then used to measure and display the frequency of the external clock. 

The 995 optical chopping head is attached to the controller by means of a 10 foot coiled cord. The precision etched blade is fully enclosed for protection from inadvertent damage. An optional exposed  or open head version is also available.

There are two apertures on the chopper head and two sections on the blade for the high and low frequency ranges. The aperture diameter is 15 mm with a slot width of 4.5 mm for the 30 slot section and 30 mm for 3 slot section. The small 4.75 inch square outline and two inch maximum depth of the chopper head permits easy integration into compact optical setups. Dual #8-32 mounting holes permit the apertures to be placed at a height as low as 0.75 inches above an optical bench, or with the included 1/2 inch rod and stand, as high as 13 inches above the mounting surface.