... power off Save powerBuilt-in RF module supervision Built-in RF module status detection Reset RF module when it out of serviceReset ... models can be selected. ProductModel NoteGSM MODEMH6221-TSRS-232 Interface, Siemens TC35i module inside, 900/1800Mhz Dual band. +5VDC, +7. 5~ ... +5VDC, +7. 5~26VDC Optional. H6221-SRS-232 Interface, Siemens MC39i module inside, 900/1800 Dual band. Either +5VDC or +7.5 ...