The power source enters the switch box (SB1) where the neutral is spliced through to the light fixture (F1) where it is spliced to the light (LT1) and, via cable C3, to the second light LT2. The hot from the power source connects to the 2-way switch (SW1) where it can be switched to the hot terminal of the light LT1 and spliced through to LT2 via the cable C3.
The power for the circuit joins the light fixture F1 via the cable C5. The neutral connects to the light (LT1) and is spliced through to LT2 via the cable C4. The hot from the power source is spliced through to the common terminal of the switch (SW1) via cable C1.
The travelers from the switches, via C1 and C2, are spliced through the fixtures,and joined by cable C3.
Shown below are two fixtures between 3 way switches.
The power source is via the switch box SB1 and a 3-wire cable (C1) runs from there to the first fixture (F1). Two, 2-wire cables (C3 and C4) run between the fixtures, and a 3-wire cable (C2) runs from the second fixture (F2) to the second 3 way switch (SW2).
The hot source is connected to the common terminal of SW1. The neutral is spliced to the white wire feeding the first fixture, via cable C1,where it is spliced to the neutral of both lights. The traveler wires from the two switches pass straight through the fixtures via cable C3.
Here we have multiple lights controlled by 3 way switches.
The hot from the power source (cable C1) connects to the common terminal of the first 3-way switch (SW1) and the neutral is spiced, in the switch box SB1, through to the second 3-way switch (SW2) via the 3 wire cable (cable C2, that also carries the travelers that connect the two switches) where it is spliced through to the first fixture (F1) and connects with the neutral of each light. In the same way, the hot from the common terminal of the 3-way switch SW2 connects to the hot terminal on each light via cable C3 (spliced in fixture F1).
The power, cable C1, joins the circuit at the light fixture F1. Here the neutral connects to the light F1 and is spliced through to light F2. The hot from the power source is spliced through both fixtures and terminates at the common terminal of SW1 via cable C3.
The travelers of each switch are connect together using cable C4 (taped white and red wires).