control consisted of range measurements and calculation of the submarine's course and speed. The aiming point was then manually determined by rule. Later, mechanical computers were used to solve the fire control problem with electrical indication of weapon readiness. Today the weapon firing process is carried out by digital computer with elaborate displays of all relevant parameters. ASW Countermeasures The main countermeasure the submarine has is stealth; it tries not to be detected. Against the ASW weapon itself, both active and passive countermeasures are used. The former may be a noise making jammer or a decoy providing a signal that looks like a submarine. Passive countermeasures may consist of coatings to minimize a torpedo's sonar reflections or an outer hull to provide a stand-off from its explosion. The anti-submarine weapon has to overcome these countermeasures. See also Anti-submarine net Magnetic anomaly detector References Bibliography Blair, Clay, Silent Victory (Vol.1), The Naval Institute Press, 2001 Lanning, Michael Lee (Lt. Col.), Senseless Secrets: The Failures of U.S. Military Intelligence from George Washington to the Present, Carol Publishing Group, 1995 Preston, Anthony, ''The World's Greatest Submarines", Greenwich Editions, 2005. External links Early British torpedoes US Naval Weapons Naval warfare Projectiles