Smartphones contain sensors such as a  to measure the magnetic field used in its digital compass.  sensors detect the presence of an object when the object enters into the sensor’s field. A  is responsible for measuring the atmospheric pressure of the environment. An  is used to identify the orientation of the device.

The text seems to be incomplete, as there are missing words in the sentences. However, I can provide the general information based on the context.

1. Smartphones contain sensors such as a "Magnetometer" to measure the magnetic field used in its digital compass.
2. "Proximity" sensors detect the presence of an object when the object enters into the sensor’s field.
3. A "Barometer" is responsible for measuring the atmospheric pressure of the environment.
4. An "Accelerometer" or "Gyroscope" is used to identify the orientation of the device.