During a Phase, the system would get quiet as no relays were getting orders and the 35-type Teletype would ring its bell and print a series of P's as long as the phase lasted.
During a Phase, the system, normally roaring with the sound of relays operating and releasing, would go quiet as no relays were getting orders. The 35-type Teletype would ring its bell and print a series of P's while the phase lasted.