@rbw156 wrote:
The extension is on the left hand side (blue wires).
That one is correct.
On the right side, disconnecting the capacitor converts it from a master socket to an extension. It can be done if they did not have dual extension socket handy.
The capacitor in a master socket is used in conjunction with a resistor, to present the correct test conditions when no phone is plugged in.
Having two capacitor/resistor connections give the wrong reading.
