Schematics | Airbag System Basis Chip (SBC) with PSI5 In this design, it features the Peripheral Sensor Interface 5 (PSI5), which is the most efficient standard interface of sensors and electronic control units in automotive. It supports complete airbag system that includes system power mode control, supplies for squib firing, satellite sensors, and local Electronic Control Unit (ECU) sensors and ECU logic circuits. Car airbag system – design & function | HELLA The safing sensor is responsible for preventing the airbags being deployed unintentionally. It is series-connected with the front sensors. The safing sensor is integrated into the airbag control unit. It comprises a reed contact in a resin-filled tube and a ring-shaped magnet.