The hydrophones, a relic of cold-war submarine tracking, picked up this signal again and again during those summer months, then it was never heard again.
The submarine surfaced suddenly and flashed a signal lamp at the ship indicating an imminent attack.
那艘潜水艇突然浮出水面，对着这条船闪着信号灯，表明攻击在即。
3
Based on signal detection theory, the real-time leakage detection problem of submarine pipeline was discussed, by means of the observed series of mass flow difference of pipe.