[1] In 1968, the voice-activated radio dispatched alarm (VARDA), was invented.
It is a portable device that, when activated, will broadcast a message to the dispatch channel, allowing officers to immediately respond to the scene for further investigation.
Although the VARDA was originally designed for law enforcement applications such as repeat break-ins, domestic violence issues and metal/equipment theft, its concept has been adapted over time to address a variety of needs in the private sector.
[1] This type of alarm is installed for special monitoring at the location of recent burglaries.
When the alarm is activated, it will set off a voice message directly over a radio frequency (generally a non-primary frequency), repeating the message several times.