Article does say that sign stealing is believed to be everywhere, both analog and advanced tech. Athletic has some sources from 2017 saying that the Astros stole signs using cameras. [Sources include former pitcher Mike Fiers. Danny Farquhar is quoted as having recognized that the Astros were stealing signs when he was on the mound facing the Astros].
Looks like they don't have any info on whether other teams have been "caught" or not, just the Astros.
Which means we're not sure if this does happen throughout MLB, or if people just generally already dislike the Astros and so are willing to talk about them more.
Astros' system in 2017 is alleged to be a camera placed in center field, aimed at the catcher.
Camera feed was linked to a monitor in the tunnel between the dugout and clubhouse. Astros employees/players would look at the feed during games.
If deciphered, the Astros would allegedly then bang on a trash can in the dugout. Sound would carry to the field, tipping off for an offspeed. This wouldn't be done at away games, obviously.
Sources are split on whether this happened in the postseason. Some said it did, some said it didn't. Noise level during the WS also may have rendered this ineffective.
Fiers says that the system wasn't used by every player on the team.
Source says that an Astro player once complained about the system not working on a particular day.
Source claims that a player said that they were looking forward to getting back home so the system could be used.
Source claims that, during a game, the Astros became concerned that they'd be caught, so the screen was hidden mid-game.
Astros apparently believed that they're justified because other teams were probably doing stuff too.
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