Assertion: disc | /r/MadeOf | an abrasive
Facets:
value: at the time
type: TEMPORAL
Source sentences:
text: At the time the LP was introduced, nearly all phonograph records for home use were made of an abrasive (and therefore noisy) shellac compound, employed a much larger groove, and played at approximately 78 revolutions per minute (rpm), limiting the playing time of a 12-inch diameter record to less than five minutes per side.