In order to use this system, the sound mixer used an intercom to the sound recordist to tell him to "roll", or start the system. Since this was a very mechanical system, it took some time to start and get up to proper speed. When proper speed and synchronization was reached, the recordist would use the intercom to announce, "Speed" and the sound mixer would relay that to the director and crew on the stage. The expression is still used, but now simply means, "Sound is recording".