This is a simple yet effective resistor decade box. The resistors are connected in parallel with the SPDT/SPST switches. The resistance is the sum of all switches opened(NOT CLOSED!). When resistors are in series the resistances add up. $$Rt=R1+R2+R3$$ And when they are in parallel the total resistance decreases: $$Rt=\frac{1}{\frac{1}{R1}+\frac{1}{R2}+\frac{1}{R3}}$$ Rt is the total resistance …
