An obvious interruption may be detected from chronological evidence showing that direct transmission was impossible or unestablished: for example, the alleged teacher died before the student was born, or reliable information excludes their meeting.
Dates of birth and death, travel records, residence, listening sessions, and generations of teachers and students help identify such breaks. Citing an earlier scholar's work is not itself proof that the later person heard directly from that scholar.
Distinction: when nonmeeting is historically plain, the gap is obvious; when a direct relationship appears possible but a particular intermediary may be concealed, the question becomes one of hidden interruption.