Just turn it on and clear away from the area. An audible alarm and red lights will alert you to an anomalous presence.
Close proximity is required to set off the device, so there is much less of a chance of false alarms.
 
The device gives off a field of energy which, when broken, will set off the device. The field can be broken by touch or an EM interference.
 
A Ghost Hunting Essential at a NICE Price!
 
Uses 1 x 9volt battery (included)