With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Craig Middlebrooks is a fictional person from a sitcom on NBC.
text_B: In physics and engineering , the envelope of an oscillating signal is a smooth curve outlining its extremes .. physics. physics. engineering. engineering. oscillating. oscillation. signal. Signal ( electronics ). The envelope thus generalizes the concept of a constant frequency .. frequency. frequency. The figure illustrates a modulated sine wave varying between an upper and a lower envelope .. sine wave. sine wave. The envelope function may be a function of time , space , angle , or indeed of any variable .
not_related.