“Nagra SNST, a miniature reel-to-reel audio recorder optimized for surveillance applications, circa 1975.
Slightly larger than two iPods, the mechanism runs virtually silently for six hours on two AA batteries, and can record about two hours of voice-grade stereo audio on each 2.75 inch reel of 1/8 inch wide tape. The device is operated with a single switch, with recording or playback selected depending on whether a microphone is attached. Rewind is via a retractable hand crank (the “T” shape between the two reels). A separate amplifier/speaker post-processor (not shown), called the “SNST-DSP” (an anachronistic misnomer, since it’s not digital), filters and EQs the recorded audio for high-intelligibility playback.”