How does a telescopic luggage handle work?

The retractable handle on my luggage is locked open. It is the lower stage that is locked, not the upper stage. Delsey ended up sending me a whole new suitcase - thank you very much! But, my technical curiosity has me wondering how I could fix the broken handle, and for that matter how does it work. I found this explanation in youtube, which explains the upper section nicely. But, that does not explain how the lower telescopic section locks and unlocks, since that rod is only pressing down on the upper section.