USGlobalSat -BU-355-S4 SiRF4 GPS Receiver with USB or serial Interface Chipset: SiRFstarIV , Interface: USB/ serial Form Factor: End-User Serial Reciever Tracking Sensivity: -163 dB / Channels: 48 Channels all in view tracking Acquisition: Hot Start 1 Sec., Average  Warm Start 38 Sec., Average  Cold Start 42 Sec., Average Dimensions : 2.08 x .75 inch / 53 x 19.2 mm