The Guitar Wiring Blog – Diagrams and Tips: How Does a DPDT Switch Work? (DPDT in guitars) from The Guitar Wiring Blog

You can use a DPDT-SW (Double Pole, Double Throw) in your guitar wiring in many ways. You can base many types of tone switches on this thing. You can use it as a pickup selector. It can change the coils in your guitar pickups (series / parallel, split humbuckers, reverse phase, on-off, etc.). Creating a switchable signal bypass or loop is also a good part.

This diagram shows you DPDT connections in some popular examples:

Direct-Through Strat Mod (Bypass)

On-board effects loop control

Custom wiring for Explorer, Flying V, ML, Razorback (Pot picker)

Dick Dale Stratocaster wiring (‘Bridge + Middle’ pickup activator)

George Lynch’s guitar pickup selector

Gibson Les Paul Jr and SG Jr Wiring Mod (Sound switch)

Altitude vent switch

Easy guitar wiring without pots (Phase sw, “on-off” recording selector)

A DPDT switch can go through part of a really handy guitar tone control. These with toggles are more robust and comfortable, but they cost an additional space in a guitar body. Push pulls are usually less convenient, but you don’t need any extra spots / holes to use them – you just have to swap them out with your old pots.