A "transmitter coil" refers to a device that generates and sends out electromagnetic waves, allowing information or power to be transmitted wirelessly. Full definition
The charger also uses a 7.5 - watt transmitter coil, resulting in fast wireless charging. (t3.com)
A series of transmitter coils buried under the skin behind the ear power the chip. (discovermagazine.com)
For the fastest wireless charging possible, check out the Belkin Boost Up, which boasts a 7.5 - watt transmitter coil that's perfect for iPhone X and iPhone 8. (cultofmac.com)