Many of the patrol vehicles for the LVMPD, Henderson PD, and NLVPD have direction finding equipment in their vehicles for detecting low power transmissions originating from "B-Packs" which are very small transmitters placed in selected money packs located in the cash drawers of many bank teller windows. When the wad is lifted out the transmitter is automatically activated. This method of tracking some bank robbers has worked very well in Las Vegas for many years. I remember many years ago back in the 90s' when a motor home was stopped by the LVMPD on Hollywood BLVD on the side of Sunrise Mtn and a suspect was arrested for bank robbery. The B-Pack transmitter worked as designed. Another incident involved an on duty postal worker in his mail truck that held up a bank during his lunch hour and tried it at a second bank without success. He was tracked right back to his postal branch that he worked out of and was arrested. Another success. Hand held tracking devices are available if the signal is determined to be coming out of a large building. The four antennas may be dual purpose, tracking lo-jack and tracking B-Pack signals.