Another issue with springed terminal in DC Jack

This is a copy of the last message posted in "Simple Power Jack Question". The thread is continued here

Thanks a lot you two for the quick answer. I tried looking at the manufacturer's website looking for this simple explanation... but this kind of info is too elementary for being there. However, it gotta be somewhere...

1. what kind of book or subject does an engineer takes for learning this kind of stuff?

I kept looking for the applications of this jack and I found something kind of useful (but still I didn't understand quite well).

2. Please take a look and give me your opinion:



My guess is that the person who designed this was trying to get power from two sources: external adaptor and internal battery. The thing is that I believe when the adaptor is plugged, it is shorted with the battery (since pin 3 is always attached to the battery). Is this an error in the design?

I have made what I think is the correction of the previous image schematic. However, the third pin in jacks is a new topic for me.

3. Can it be used in a situation like this?



4. What happens during the short time in which the external adaptor is coming into the jack and barely touches the pins 1 and 3 but the pins 3 and 2 are still closed (that is electrically shorted?. Whould this jeopardize the life of the battery in a long term?. Is there some sort of staggered mechanism that impedes this from happening?.

Thanks again for your attention.

When you carefuly look at the push-fit-plug you will find out that the first section is madu of a plastic .. see picture below ..
This section is designed to open contacts ..
There is no way (unless connctors are damaged) you can shorten outputs 2 and 3 while pushing plug inside socket, hence your battery and external power supply are "safe" ..

Regards,
IanP