Beware the 3.5mm stereo jacks when wiring up to make a download connector (to take the Picaxe AXE027 USB-to3.5mm cable for example).
There are five outputs. The centre one is simple, but be careful with the others. The two outer pairs are commoned together when the jack is absent, but not when it is present.
Unless you want to switch based on presence, then make a permanent connection between the two pins of A and another permanent connection between the two pins of B. This reduces the danger that you end up with missing connections that test OK with the jack removed - a potential source of much misery (from bitter experience!)
