silent alarmn.
/ˌsʌɪlənt əˈlɑːm/, /ˌsʌɪln̩t əˈlɑːm/, U.S. /ˌsaɪlən(t) əˈlɑrm/ An alarm made without a sound; spec. a burglar alarm that gives no audible signal at the scene when triggered, but instead alerts a remote monitoring station.In quot. 1858 as a call to arms signalling a fight.
ΚΠ
1858 N.-Y. Times 22 Mar. 5/1 The fight between firemen..was resumed at 8½ o'clock last evening, at which hour a silent alarm for the Seventh District was given.
1958 Sci. News Let. 18 Jan. 48/3 The alarm is designed for three-fold use: sounding off in its immediate area, flashing a silent alarm at a police station, and signaling a guard station.
2019 East Bay (Calif.) Times (Nexis) 27 June Officers responded at 4:07 a.m. to a silent alarm indicating a..burglary was in progress.
This entry has been updated (OED Third Edition, September 2020; most recently modified version published online March 2022).
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n.1858