First-part device: RF Transmitter + GSM Module(no data transmission, only stand by) + battery(from mobile phone) + 220V power supply
Second-part device: RF Receiver with the indicator of level of a signal. It is used for the the step-by-step equipment search in a zone with radius of 300-500 m. User rotate the aerial and look's for a signal maximum on the indicator, and we go towards increasing signal.
Now we need sample device and then 30 such devices(first type). and 2 Receivers