I said that there was a transformer which stepped up the voltage from 3V to 24V, and that the switch controlled the supply of power from circuit A to circuit B, since there was no power source in circuit B.
Dont know if it is right, but thought I would put my ideas here anyway...
There was a few questions that I had no idea about, like the twisting of unshielded wires or something. Totally bullshitted that one.