The Giants' decision to use a walkie-talkie during the fourth quarter of the team's 10-7 win over the Cowboys on Sunday is reportedly being investigated by the NFL.

According to Troy Hughes of CBS Sports radio 105.3 the Fan in Dallas, the Cowboys filed a formal complaint this week and asked to the league to investigate the situation.

Under NFL rules, coaches aren't allowed to use any type of two-way radio during a game. Giants coach Ben McAdoo broke that rule in the fourth quarter when he starting using a walkie-talkie after the radio went down in Eli Manning's helmet.

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Ben McAdoo had a walkie-talkie in the fourth quarter. NBC/NFL

The reason you can't use a walkie-talkie has to do with the spirit of fair play. When a quarterback is wearing his normal helmet, the NFL cuts off all radio communication with the helmet once the play clock hits 15 seconds. That means that the quarterback doesn't have any communication with his coach in the final 15 seconds before a play is run.

However, since McAdoo had a walkie-talkie, there was no way for the NFL to enforce the 15-second rule.

According to ESPN.com, which also reported the investigation, the Cowboys didn't even technically have to file a complaint because the NFL was already looking into the Giants' potential violation of the rules.

Cowboys executive vice president Stephen Jones clearly wasn't happy with the fact that the Giants were using walkie-talkies on the sideline.

"We don't comment on things like that, but it's obvious to everybody what happened, and my understanding is it's being looked into and handled," Jones told ESPN.

On the Giants' end, Manning said his radio was only down for about four plays during the fourth quarter, which was when McAdoo used the walkie-talkie.

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Here's a better shot of Ben McAdoo's walkie-talkie. NBC/NFL

"I just wasn't getting anything, so I had to run to the sideline to get the plays," Manning told the New York Post this week. "Four plays maybe, we don't have signals for stuff. It happened to be all run plays. If it's pass plays, [backup quarterback Ryan] Nassib or somebody could signal them to me. I had to run to the sideline, sometimes he was giving it to Odell [Beckham Jr.] right there, and Odell would run to me and get the play in. Like high school.''

Manning admitted that he wasn't sure if the plays were coming in from the coach's radio or from McAdoo's walkie-talkie.

"I don't know when he was on the walkie-talkie or not," Manning said. "I just knew it was back in my ear, and we were going."

According to NBC sideline reporter Michele Tafoya, the Giants' equipment manager was the one who decided to have McAdoo use the walkie-talkie.

"The equipment manager went to the backup helmet, tried to get that working, realized the only way they could communicate with Eli was with that walkie-talkie, so the equipment manager ran to McAdoo, handed him the walkie-talking and there we go," Tafoya said during the broadcast.

This is the second time in two weeks that the Giants have been involved in a controversy. During their 24-14 loss to the Steelers in Week 14, the Giants accused Pittsburgh of using deflated footballs.

If the Giants are found to be in violation for NFL rules for walkie-talkiegate, any punishment would be at the league's discretion.