A near field communications (NFC) device is disclosed that detects a presence of another NFC capable device within its magnetic field. The NFC device provides a detection sequence having one or more detection signals to its environment. The NFC device observes the detection sequence as it is being provided to its environment to recover one or more observed detection signals. The NFC device determines a difference between the observed detection signals and one or more previous observed detection signals and/or the detection signals. The NFC device characterizes the difference as resulting from changes in the environment when the difference is linear or as resulting from another NFC capable device being present within its magnetic field when the difference is non-linear.