In general, you don't need to connect your base stations to each other with the sync cable.
However, if you have a hanging object from the ceiling that is above the play area or if your base stations need to be positioned low such that your head or hands block the bases from seeing one another, this may affect the syncing of the base stations. You'll need to attach the sync cable.
- Attach the sync cable to both base stations and make sure to route the cable outside of your play area.
- Press the Channel buttons on the back of the base stations so that one base station is set to channel "A" and the other is set to channel "b".