These are radio walkie-talkies. As long as only one handset transmits at any given time, there is no limit to the number of devices listening on the same channel. With 12 devices it's only a matter of following proper radio etiquette to make sure there is no uncontrolled chatter. Motorola TLKR radios also feature a group calling mode. To my knowledge up to 16 devices can join such a group as the available ID numbers are between 1 and 16.