Rezence (pronounced reh-zense) was an interface standard developed by the WiPower (A4WP) for wireless electrical power transfer based on the principles of magnetic resonance. The Rezence system consisted of a single power transmitter unit (PTU) and one or more power receiver units (PRUs). The interface standard supported power transfer up to 50 watts, at distances up to 5 centimeters. The power transmission frequency is 6.78 MHz, and up to eight devices could be powered from a single PTU depending on transmitter and receiver geometry and power levels. A Bluetooth Low Energy link was defined in the A4WP system intended for control of power levels, identification of valid loads and protection of non-compliant devices.
The A4WP was formed in early 2012 with the intent to create a wireless power transfer standard to compete with the existing Qi standard. Board member companies included Broadcom, Gill Electronics, Integrated Device Technology (IDT), Intel, Qualcomm, Samsung Electronics, Samsung Electro-Mechanics, and WiTricity.
In January 2015 A4WP and the Power Matters Alliance announced that the two organizations intended to merge into the AirFuel Alliance.