SANTA CLARA, Calif. — Mark Roman is still getting used to that little voice in his ear telling him where to go and what to do.

The San Francisco safety knows he'll have to adjust to the NFL's new way of calling defensive signals with the freshly installed communication device in his helmet. At the 49ers' minicamp, Roman and three fellow safeties joined dozens of players across the NFL this weekend as the first to try out the league's next technological step forward.

Quarterbacks have used the sideline-to-field devices for years, allowing coaches to relay plays to the offensive huddle without elaborate hand signals or shuttling in the plays with substitutes. NFL owners only approved the headsets for defensive players at league meetings last month, overcoming a bit of dissent from offensive-minded head coaches.

"I didn't even know the rule had passed until they said we're going to try it with the headset," Roman said. "It's cool. It's going to help out because we aren't going to have to be scrambling to get the calls."

Only one defensive player at a time can wear the helmets with the bright-green dot on the back. While many teams plan to put the headsets on linebackers who play every down and typically call the defensive signals in the huddle anyway, the 49ers passing the helmets around and familiarizing their safeties with the whole procedure first.

Safeties Keith Lewis, Michael Lewis and Dashon Goldson also had the headset helmets Saturday, and secondary coach Vance Joseph relayed personnel groups and plays from his sideline headset.

"You can communicate with speed if you know the plays," said Roman, who's entering his third season as a San Francisco starter. "Once I hear it, I'm thinking about everybody I've got to tell, and everything I've got to do. It's real good."

Coach Mike Nolan, a longtime defensive coordinator who voted in favor of the rule change last month, is still experimenting with the best way to use the technology. The 49ers haven't decided who will wear the headsets during the regular season, though defensive coordinator Greg Manusky said it's most likely to be linebacker Patrick Willis or cornerback Nate Clements, who both rarely leave the field.

"They're all veteran players for us, and we're playing with that," Nolan said. "We're not sure how we'll utilize it, but we'll see where it goes. ... If somebody is good at calling the huddle but doesn't want the noise in the helmet, we'll do it with hand signals."

Roman and linebackers Derek Smith and Jeff Ulbrich ran the defensive huddle last year, but San Francisco's defensive sets typically aren't communicated by just one player in the huddle. The three down linemen often have different instructions than the four linebackers and four defensive backs.

Willis, the NFL's leading tackler and top defensive rookie last season, isn't sure how he'll like having a voice in his ear. In Saturday's practice, Roman got the defensive alignment from the sideline and then gave it to Willis before the 49ers met in the huddle, where Willis relayed it to the team.

"If they were to ask me to wear it, I would," Willis said. "Normally, we just look to the sideline and get the call. For us linebackers, from Day One we've got to talk to the D-line and the DBs. We all just kind of go hand in hand. The one thing we're working on in minicamp is really communicating."