1ራሱን is a mobile terrestrial digital audio/video and data broadcasting service in Japan, አርጀንቲና, ብራዚል, ቺሊ, ኡራጋይ, ፓራጓይ, ፔሩ, and the Philippines.

1 seg is designed as a component of ISDB-T, the terrestrial digital broadcast system used in those countries, as each channel is divided into 13 ክፍሎች, with a further segment separating it from the next channel; an HDTV broadcast signal occupies 12 ክፍሎች, leaving the remaining (13ኛ) segment for mobile receivers, hence the name, “1ራሱን” ወይም “አንድ Seg”. See full seg.