With band-pass filter tuned to 56 kHz and monotonic sensitivity vs. frequency response curve from 30–54 kHz, TSSP4056 provides proximity sensing from 10 cm to 2 m in various systems. This fixed-gain IR sensor, which may also be used as reflective sensor, detects modulated pulses from separate IR emitter with sensitivity of 0.4 mW/m². Offering readings in under 5 msec using successive approximation techniques, sensor determines distance by varying carrier frequency used to drive emitter.