Incoms take the form of a small white earphone with a microphone attached to it. The earphone is usually attached to the left ear and has a decor on it to look like Death's mask.
Like ordinary headsets, they're capable of broadcasting and receiving audio clearly, with Kilik Rung and Liz Thompson both praising the Demon Tool for it's ability.
The three Japanese kanji used in the word 'Incom' are a part of the verb 'to hide' (隠し Kakushi), the word for 'meeting' (会 Kai), and 'nothingness' (無 Mu). This explains how the Incoms allow 'hidden conversations/meetings' through its communication abilities. The kanji for nothingness is connected to the Japanese word for 'wireless' (無線 Musen).