How the IP rating system actually works, what IPX4, IPX7, and IPX8 each certify, and what 'waterproof' can and cannot legally claim.
- IP ratings describe tested protection against solids and water; the first digit covers dust, the second covers water.
- IPX7 certifies immersion to one meter for 30 minutes; IPX4 certifies splashes from any direction, not submersion.
How air-pulse and pressure-wave devices actually generate sensation, and what the popular 'suction' description gets wrong about the mechanism.
- Air-pulse devices use a sealed chamber that rapidly changes air pressure around external tissue; they do not vacuum or pull tissue inward.
- The sensation comes from oscillating pressure, not from contact friction or vibration.
How eccentric rotating mass and linear resonant actuator motors differ, why frequency and amplitude matter more than mode count, and why rumbly output survives muffling.
- Two motor architectures dominate: eccentric rotating mass (ERM) and linear resonant actuator (LRA).
- Rumbly sensation comes from low frequency and high amplitude; buzzy comes from high frequency and low amplitude.
Why app-connected devices drop, how BLE differs from proprietary RF, what degrades under poor networks, and what privacy an app actually introduces.
- Bluetooth Low Energy was built for sensors like heart-rate monitors, not real-time interactive control, which is why latency and dropouts are common.
- Proprietary 2.4GHz links for a local remote often beat BLE because they skip the smartphone operating system's overhead and permission layer.
Why a '10-speed' label hides a narrow range, what frequency and amplitude each measure, and how to compare two devices with numbers instead of adjectives.
- Intensity is the combination of frequency (Hz) and amplitude (counterweight travel), not the number of modes on the box.
- A '10-speed' control is usually ten voltage steps across one motor's narrow hardware range, not ten distinct power levels.