The "Ascender" is a small rope climbing robot, which is not unlike an automatic yo-yo. Once attached to the bottom of a rope (actually fishing line), it can climb to the top and back down. It is light-activated (that is, it starts and stops when a light shines upon it). The speed and distance of the climb are both adjustable.

It was designed and built for the 2nd International BEAM Robot Olympic Games in Toronto, Ontario in 1993. It was built for the rope climbing event in which robots raced one another up and down a fishing line of 1 meter in length.  In this context, it won the silver medal in rope climbing in 1993 and won the gold medal in 1994.

The main difficulty that I encountered was that the motors drew a lot of amps from the 9v batteries which caused the logic circuits to occasionally overheat and shut down. Since the speed of the robot was adjustable, I ran it at slow speeds to avoid overheating. Also, flashes from photographers at the Olympic games caused the robot to suddenly stop climbing (I hadn't thought of that).   Here is a simple schematic of the electronics that allows the robot to climb to a specific height based on the number of rotations: