OOC : This Article refers to the Spectre of War theme, (Amanda Wheatly's theme).
The 'Battle Beep', also known as the 'Death Beep', is the audible tone or series of tones emitted by a large number of Western firearms (and some late model Eastern ones), indicating that a built-in personalized safety system has been initalized and paired with the coded transmitter worn by the firer; most weapons utizling PSSes require this initalization before the weapon can be fired at all, to ensure that the weapon will not fire when used by unauthorized personnel.
The most widely known Battle Beep code is from those PSS systems built into Smith-Wesson-Colt firearms, a loud, musical two-tone signal, the second of a higher pitch than the first, that emits quickly upon intialization; Western European arms manufactuers built most weapons with a tri-tone signal that performs the same way, while the few Chinese weapons that utilized it emitted a single tone. A corresponding 'Peace Beep', indicated that the weapon had been disconnected from the PSS and placed in a 'safe' mode, usually has the tone system reversed, going from a high to low tone in multi-tone systems, and simply a lower tone in single-tone systems.
The first weapons utilizing PSS systems were primarily used by late-War URBPAC teams as well as most militarized law enforcement; these first weapons, while achieving their objective in keeping usable automatic weapons out of paramilitary criminal elemants, suffered poor construction, poor materials, and an array of technical bugs ensured that the weapons often mantained only intemittant contact with receivers after pairing; consequently, the practice was to initalize the connection with as little time as possible before engaging a target, resulting in the battle beep sounding shortly after a SWAT team breached a building, or a police officer drew their weapon to engage a combatant. As the technology became more stable, it was exported out to military units, where the battle beep was heard in mass amounts during customary weapon checks by personnell. Late-model Western 'pulse' weapons incorpated the inital charging of the electric firing mechanism with the initalization of the PSS system, with the same sound.
Because of it's early type of use in law enforcement and it's widespread use by the Western militaries in the late-war, the battle beep itself has become a trope in post-War fiction, pop culture holding it next to, and sometimes even superceeding, the act of pumping a shotgun, pulling a charging handle, or chambering the round in a semi-automatic pistol, as a loud, recognizable sound that a weapon is live and capable of killing a target.