Then you had a different model. The one bit I know for certain about mine was that the cliff detector was optical. How? By noticing one day that the black area

Then you had a different model. The one bit I know for certain about mine was that the cliff detector was optical. How? By noticing one day that the black areas of my striped carpet were inexplicably accumulating more dirt than the rest of it. Took me some time to find out that the robot treated black floor as "hole in the ground" and made an active effort not to drive over it... > Mine also regularly blew through the IR "walls" and got stuck under a dresser, waiting for me to return home with it's familiar "help" beeps. Yup, got those often enough as well...