How do i connect this socket?

Hi, im not sure how to connect a 2.5mm power supply socket to the pcb i have.
I'ts a project from a magazine. The schematic shows 3 terminals on the socket, as i've shown on the top half of my sketch.
The pcb has 2 of the terminals connected together, as i've shown on the bottom half of my sketch.

I've attached pics of the socket.

I have used my multimeter to measure resistance between points, the results are:

with no power lead connected:
A-B = open circuit
A-C = open circuit
B-C = short circuit

with power lead connected
A-B = open circuit
A-C = short circuit
B-C = open circuit

Which points on the bottom half of my sketch are A, B and C?

You have a "selfish" type female conector.

Is your 2.5mm plug connected to anything? Your measurements are a bit strange, because with or without the plug, the "A" terminal should never make contact with any pins. (Only if your 2.5mm plug is already connected to the seconday of a transformer).

"A" terminal will never change, so one wire will go there.

You are going to play with "B" and "C".
If your plug is already connected to a transformer, then the other pin you are going to use is "C".

"B" terminal will only work when there is no plug.

thanks for replying hayato.

Yes, my plug is connected to a transformer.
Thanks i now understand how the socket is connected