Dpac12099 - Filter Question Plus Use Of Switch By Spec Plate

I have the Owner's Use and Care Guide and on Page 9 there are instuctions which are confusing regarding the Cleaning of the Air Filter. As follows: #1 - "To remove air filter: Pull the air filter cover upwards in the (blah, blah...) (Fig 4) and remove air filter." In the (Fig.4) diagram it does look like there is a cover and a filter inside to be removed? Thus the confusion! I only have a plastic "cover" with little tiny air-type ventilation holes that does remove in the manner described. That is all I have ever had. I assumed this was the filter until I re-read the Maintenance page of said Guide. This is when I paniced...thinking i have been operating the unit without a real filter. Also, there is no mention in the Guide as to the function of the switch below some very small air holes (I presume they are air holes?) and beside the Specification Plate in the back bottom half of unit? I only just noticed it and can only guess that it has something to do with the "air holes"? As to what function they have is only guesswork on my part. Other than these 2 questions, i am very pleased with the unit. I would appreciate an answer to these 2 mysteries as soon as possible as I do not want to cause any damage to my life-easing machine. I am on disability and could not possibly afford another unit. Thank you in advance. Bonny