The sirens blaring at Browns training camp come without notice or warning, but players and coaches know what they mean.
"When you hear the sirens," linebacker Christian Kirksey said, "you're ready to step it up a notch."
"It means it's game time, man, it's time to go," defensive lineman John Hughes said.
"Whenever the siren goes off," Hughes said, "it means we have a live period so we get to actually hit and tackle and everything."
And after a spirited practice Sunday afternoon, it seems like a well-received period that gives coach Hue Jackson and the coaching staff a look at what kind of team they have three days into camp.
"I think our guys liked it and respected it and I think it's different. I know it's a little bit different, you know, than maybe what they've been accustomed to," Jackson said, "but I think it's what it's truly going to take for us to have a really good football team."
Indeed, the purpose of the live sessions is two-fold. The first is a chance for the Browns to practice and master the fundamentals of tackling.
"As a defensive player, when you hear the sirens, you get an extra pump," Kirksey said. "You know it's a live period, you finally get to tackle and that's what we need to work on as a whole — just tackling, getting guys on the ground."
After two days of closed practice, the Browns welcomed fans to the training facility in Berea for the third day of Training Camp.
The second objective, Jackson said, is to help the Browns establish something of an identity over the next month.
"I'm looking for a team that's very relentless, that can go after each other. Because, again, as I told our players I have to find out who we really are, what's going to truly be our identity," Jackson said Saturday.
"One thing we talked about last night is all the really good football teams in the National Football League, they have an identity and we don't want to wait to find out what our identity is. We've got to establish it now, and so you only establish that by grinding a little bit."
The Browns can work toward that mission through live sessions, among other dynamics, that seem to reinforce the energy and fast pace Cleveland's practices so far.
The drill also keeps everyone — players, coaches, reporters, fans — on their toes.
"They don't know when they're coming," Jackson said. "They just can show up at any time."
"That's what the siren's for."