OVERVIEW: Underwater sensors installed on surface ships, providing detection, tracking, and classification of underwater threats using both active sonar pings and passive listening.

GENERAL DESCRIPTION: These sonar systems combine active transmission of sound pulses with passive reception of underwater acoustic signals to locate, identify, and engage submarines, torpedoes, and other underwater targets at close to medium ranges. Operating primarily in the medium frequency (MF) band, they enable rapid target acquisition and fire control support in anti-submarine warfare (ASW). Installed in hull-mounted or variable-depth sonar arrays on surface combatants, they provide vital situational awareness and engagement capability in littoral and open-ocean environments. The dual-mode capability allows operation in passive mode for stealth or active mode for precise ranging and targeting.

ROLE SUMMARY:
Category: Hull-mounted active/passive attack sonar
Primary Use: Detection, tracking, and fire control of underwater threats
Function: Short-range underwater surveillance and engagement support
Platform: Surface combatants including frigates, destroyers, corvettes
Export: Widely fielded among NATO, allied, and some non-aligned navies
Integration: Integrated with combat systems, torpedo launchers, and countermeasures

Type: Active and passive sonar
Processing: Real-time active ping transmission and passive signal analysis
Sensor Type: Hull-mounted or variable depth sonar transducers

See Specific information under [Sensors/EW] section.

SOURCE:
NATO ASW Doctrine and Equipment Reports
https://en.wikipedia.org/wiki/Active_sonar