Fairlie’s done a number of projects involving the Flipper Zero, a sort of Swiss Army knife for electronic experimentation — RFID, infrared, radio transmission; you name it, the Flipper can do it.

Source: https://jalopnik.com/how-to-turn-red-lights-green-1850129880

This is as a result of the launch of the Digital Audio Broadcasting system which is to ease up the congestion and to allow for more space to radio transmission.

Source: https://theheraldghana.com/ghana-kick-starts-use-of-digital-audio-broadcasting/

Though he speaks with Tomura Shigaraki through a radio transmission during the League's multiple schemes, he is formally introduced much later in the series.

Source: https://gamerant.com/my-hero-academia-villains-best-introductions-ranked/