Which kind of alarm does not produce a sound but alerts authorities?

A burglar alarm silent is a type of security system designed to alert authorities without making a sound. This is beneficial in situations where a noise alert could tip off a burglar that their presence has been detected, allowing them to flee before law enforcement arrives. Silent alarms often send a signal directly to a police station or monitoring center, enabling a discreet response. This method of alerting helps ensure the safety of individuals on the premises while allowing police to intervene before a potential crime escalates.

In contrast, audible alarms are intended to deter intruders by making loud noises, which can alert both the occupants and neighbors but may not effectively prevent an intruder from escaping. A manual alarm typically requires a person to activate it, which may not always be possible in an emergency. An alert system could refer to various systems, and it's not specific to silent alerts that notify authorities without sound. Hence, the burglar alarm silent is the most precise choice for this question.