Sign stealing has been around forever.
Runners on second base watch the catcher so they can tell their batter what to expect from the next pitch. That’s legit. But, watch (from somewhere else) with binoculars, and it’s illegal. In the 1950’s, the New York Giants used a telescope. That was illegal too.
To battle this, complicated signals are used to throw off opponents: sets of signals that contradict each other and confuse anyone who is trying to decode them–all of which take time. Pace of play is a modern concern for baseball; the long series of fake signals don’t help.
the rules (reported by Boston Globe)
Sign-stealing is not prohibited, but the use of electronic devices in dugouts (with a few exceptions) is not allowed. A preseason bulletin was passed out to all MLB teams in 2017 with the this clarification:
- The use of electronic equipment during a game is restricted. No Club shall use electronic equipment, including but not limited to walkie-talkies, cellular telephones, laptop computers or tablets, to communicate to or with any on-field personnel, including those in the dugout, bullpen, field and, during the game, the clubhouse.
- No equipment may be used for the purpose of stealing signs or conveying information designed to give a Club an advantage. Laptop computers and hand held devices are not permitted on the bench or in the dugout.
- The only exceptions to this prohibition are the use of a mobile phone for communication between the dugout and the bullpen, and the use of tablets in the dugout or bullpen running uniform programs, so long as such devices and programs have been approved by the Office of the Commissioner.