TESTED & Working - Radio Shack Realistic Sound Level Meter 33-2050 w/Case Manual | eBay
Retro Thing: Radio Shack APM-200 Power Meter Lets You See The Music
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Realistic, Audio Power Meter in Original Box | #352 32in-70in TV's/Monitors, Soundbars/Subwoofers, Projectors, Screens, Amplifiers, Speakers, Electronics, Large Lots | K-BID