Definition of "sepmag"

sepmag

adjective
not comparable
1. (television, dated) Having a separately magnetically recorded soundtrack running concurrently with the film footage.
  Quotations
  At the appropriate distances (28, 26 and 20 frames) ahead of the JOIN PICTURE HERE line there are rows of squares, circles and triangles which indicate the correct splicing points for 16-mm sepmag, 16-mm sepopt and […]
  1968, D. J. Corbett, Motion Picture and Television Film, page 64
  Sound for these two telecines is reproduced from conventional sepmag tape machines.
  1970, BBC Engineering, numbers 81-88, page 13