A personal alarm is used emits an audible chirp and usually a flashing LED when a particular amount of radiation has been received. The higher the radiation field the more frequent the alerts become. Personal alarms are useful as passive devices, kept in a person’s pocket alerting them if they enter an area of high radiation.
The Guardian PA is designed for the use by operators working in an area of potential danger of radiation exposure.
Roffey Bleeper Mk3
The passive radiation monitor is a low cost method of detecting high fields of radiation.