blue call
n.— «While the questioning was going on, we were assessing the baby. She was unconscious, and when we pricked the heal of her foot to check her blood sugar level, she grimaced but didn’t cry.…We were going to take Emily in on blue lights, asking control to let the hospital know what had happened and how long we would be so they could be ready. This is known in London as a “Blue Call.” I changed the channel on the radio in the car to listen for the crew putting in the blue call—that would be my signal that they were ready to go, then we set off.» —“Dreaded Call” by Steve Gibbs The World Through The Eyes of an EMT (London, England) May 19, 2006. (source: Double-Tongued Dictionary)