From the Philly Inquirer:

The Mets heard from former Phillies on their team and other clubs, including the Los Angeles Dodgers, that the Phillies use the camera to steal signs. The Mets possibly became sensitive to this after Monday’s 9-2 loss, so they changed their signs Tuesday.

Lefthander Tom Glavine threw seven shutout innings Tuesday before the Phillies won, 4-2, in 10 innings. The next day, the Mets reported that the Phils joked with them that they had changed their signs.

Without knowing how long the Phillies are accused of stealing signs, it’s particularly hard to figure out if there’s anything fishy in their hitting. But
At home, they’re hitting .285/.363/.480
On the road, they’re at .271/.347/.444

Last year, their split was
.274/.353/.462
.260/.341/.433

So it’s not as if they’re hitting dramatically better at home versus the road compared to last year.

The really telling stat would be whether the Phillies saw an advantage hitting until the other team went to using rolling signs. That’d usually be with a runner on second, though some teams are more aggressive about it depending on who’s on first or third. If the advantage went away, that’d be evidence in the Mets’ favor.

Unfortunately, as an outsider, I don’t have access to this kind of detailed splits, and when you slice data that finely, it’s often hard to see patterns for the noise.

We may also see, assuming the Phillies had a system and shut it down, the home field advantage narrow.

It’s also interesting that they traded Russ Branyan to the Cardinals a few days ago. Branyan would know if the Phillies had a system in place, but there’s no incentive for him to spill the beans, since the two teams don’t play each other in September.

Having said all that, if I were a team in the Phillies’ situation, I’d totally say things like that to screw with opponents. If they think you’re stealing signs and they go to a more complicated system, the chances they’ll cross up pitches and give up a wild pitch increase, and that’s a free advantage.

The article discusses various means the White Sox used: stealing out of the center field scoreboard, and using flashing lights and even using a loudspeaker in the dugout. But the unique part was that they

…wired the third base coaching box for sound and even gave pitcher Early Wynn an electronic receiver to use in his cap so that Manager Al Lopez could communicate with him on the mound

The coaching box harkens back to the earliest incident of electronic cheating ever (which is in the book) but for the team to wire the pitcher – I believe that’s the only instance I came across.

It gets better, though.

The White Sox even installed wires around the third base coaching box and equipped Cuccinello with a special receiver which was pinned under his uniform shirt. This enabled him to get signs from Lopez without ever turning around to look at his manager.

Billy Martin tried something like this (with funnier results) in an incident that’s in the book, but I don’t want to spoil that joke.