There are three exterior oscillators on both the Prius and the Camry: one in each front door and one in the rear bumper near the trunk/hatch. Oscillators broadcast 134.2 kHz wireless data at regular intervals, in the hope a Smart Key will hear the broadcast and respond. The Exterior Oscillators are controlled by the Certification ECU. It’s important to note that oscillators only talk; they don’t listen. Oscillators are all mouth.