If you get the "Sorry, the file cannot be displayed. There seems to be a technical issue ..." error when trying to view an image, a workaround is to click on the cog icon in the upper right side of the media viewer, and then select "Disable Media Viewer". We are aware of the problem and are looking for a solution.
The Tektronix 161 is a "Pulse Generator Module" for the 160 series modular oscilloscope system.
It produces a rectangular pulse at its output when it is triggered by a pulse at its input. When the the 160 system is used as an oscilloscope, the 161 can serve as the trigger circuit that starts the horizontal sweep. The 161 is documented in the 160-series manual.