Switch - Switch - Light - Circuit
This is perhaps the most difficult 3-way switch configuration that we will present. It presumes that the circuit continues after the switch. This is actually a quite common occurance as you may put more than one outlet or light on a circuit.
In our example here, the source comes in one of the switches. As always, the power for the light must go through both switches before it comes to the light. Also, as usual, a white wire is marked black and used to carry the load. What is more unusual about this configuration is the extra set of wires travelling between the two switch boxes. This actually ensures that the current is carried by the switch to the circuit beyond. In this case you do not want the switches controlling the rest of the circuit.
Note also that the white, neutral wire from the light is simply spliced into the neutral from the by-passing part of the circuit.
It is well to note that the examples shown on these web-pages do not cover all of the possibilities. But they should be enough to allow you to figure out what you need to do using the basic ideas behind the 3-way switch.