Vanderbilt used an electronic wristband system for calling pitches
File:Coleco Head To Head Baseball, Model 2180, Made In Hong Kong, Circa 1982 (Electronic Handheld Game).jpg - Wikimedia Commons
File:Electronic Baseball by Entex Industries, Model -8001, Red LED, Made in Taiwan, Copyright 1979 (LED Handheld Electronic Game).jpg - Wikimedia Commons
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George Kell designed an electronic sign-stealing operation more than 60 years ago - Vintage Detroit Collection
Coleco Head to Head Baseball
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MLB looking at electronic system for calling pitches | AP News
Old Handheld Video Games: Electronic Baseball 2 (1979) - YouTube
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ENTEX ELECTRONICS 1979 HANDHELD ELECTRONIC BASEBALL GAME | eBay
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Future Stars Electronic Baseball Rocket Launcher Combo Set - 1 Electronic Pitching Machine with 5-ball feeder, 1 24" telescoping bat, 5 plastic baseballs - Unisex - Perfect for all players! - Walmart.com
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Handheld video game:Coleco Head to Head Electronic Baseball - Coleco — Google Arts & Culture