1seg is a mobile terrestrial digital audio/video and data broadcasting service in Japan, अर्जेंटिना, ब्राझील, चिली, उरुग्वे, पराग्वे, पेरू, and the Philippines.

1 seg is designed as a component of ISDB टी, the terrestrial digital broadcast system used in those countries, as each channel is divided into 13 विभाग, with a further segment separating it from the next channel; an HDTV broadcast signal occupies 12 विभाग, leaving the remaining (13व्या) segment for mobile receivers, म्हणून नाव, “1seg” किंवा “एक Seg”. See full seg.