Looking at the schematic, we can see that there are high and low-capacity contactor coils. The high-capacity contactor has a contact point on it and a straight-through connection; there is a constant connection to L2 AND a contact. However, on the low-capacity contactor, there’s just a contact.

The start capacitor and relay are connected between the high and low-capacity contactor coils. The high and low-capacity contactors also both connect to L1. In this configuration, the potential relay is wired start to run, so the 5 terminal is on run rather than common, which is an unusual configuration.

Only one contactor can close at a time; that must happen to create a difference in electrical potential. In the low stage, the low-capacity contactor will be closed, and the opposite is true of the high stage. That sort of configuration essentially allows us to swap run and start. In both cases, both the start and run capacitors will be in the circuit.