Passive GSM 5.1 Monitoring System
 
Completely Passive Interception of:
Voice
SMS
 
Range of approximately 
500-1000 meters on the forward channel
20 km on the reverse channel.
 
4 Hardware Components 
MPU or Main Processing Unit
Receiver Box
5.1 Decoder Box
Antenna
 
MPU or Main Processing Unit
tandard “Lunchbox”style computer.  Typically Acme brand.   Standard Configuration is 32 channels, which allows for 192 calls at the same time. 
The MPU is where you scan your surrounding BTS
The MPU is where you choose /set which BTS to monitor
The MPU is also where all data is stored and processed.
 
Receiver 
The Receiver can be tuned for either of the below sets:
900/1800 mhz
 OR
850/1900 mhz
 
Decoder Speed 
5.1 Decoder decodes the KC of the phone.
Decoders have different speeds.
The highest speed currently decodes at 0.7 seconds.  This is the highest cost decoder as well.  For speeds like 30 seconds, and 60 seconds, the price of the decoder will decrease.
Several units can all be connected to the same decoder if you choose to.