Adding to the other answer, A is dependant on the number of pins, which is common in connector datasheets (the same datasheet is used for a series of connectors with varying pin numbers).
So A is 1mm * number of spaces between pins, B is A + 2.1mm, and so on.
So for a 4 pin connector, A is 3mm, B is 5.1mm, C is 7mm.
You can use your real-world experience with units (or seeing which unit conversion is consistent) to know whether it is inches[mm] or mm[inches].
In this case it is obviously (if you have ever looked at a metric/imperial tape measure or rule) inches[mm] because 1 inch is humongous while 0.039mm is too small to see. Furthermore, \$0.039mm \ne 1 inch\$ so the ...
Pin 1 is "positive" if your system is setup like that. THERE IS NO REASON IT COULDN'T BE NEGATIVE! "Positive Tip" is something of a common standard, but there are examples where this is not true (for example - guitar pedals pretty much are all negative-tip, positive shield)
Pin #3 is a switch that is 'normal closed'. When no plug is in the jack, pins #...
This is a Stäubli POAG connector.
For more detailled information on the product, refer to the catalogue:
or visit the website
That looks like an m3 or m2.5 broaching nut, but by the looks of it, it is not a solderable nut. It looks more like a press fit broaching nut, that is used for pressing into sheet metal or plastic. (you can tell by the corrugation on the sides which is typical of broaching nuts.)
A better way to do this is to use a solderable nut that is built for PCB's like ...
Pin 1 is negative for guitar effects pedals.
Pin 1 is positive for almost all other applications.
Don't ask me how I discovered the difference, but my son now has one fewer working effects pedal.
In both cases, pin 2, and pin 3 if used, are the other sign.