Welch Allyn RL-100 Rhinolaryngoscope - User Manual - Manual (Page 9)

COUPLING THE CAMERA TO AN ENDOSCOPE
Grasp the two tabs on the outside ring of the eyepiece coupler with
your thumb and index finger and depress. This will retract the
eyepiece retainers on the coupling side of the eyepiece coupler.
Insert the endoscope eyepiece into the coupler as far as possible
and release the tabs. The camera/coupler should be rigidly mounted
to the eyepiece.