... reliable, flexible, economical data communication services at anywhere and anytime.H6221 Series GPRS/EDGE Modem Functions1) Basic FunctionsEase to use, reliable ... inside, 900/1800 Dual band. +5VDC, +7. 5~26VDC Optional. H6221-SRS-232 Interface, Siemens MC39i module inside, 900/1800 Dual ... band. Either +5VDC or +7.5~26VDC. H6221-HRS-232 Interface, Huawei module inside, 900/1800 Dual band ...