1# telephony_data.h 2 3## Overview 4 5Defines C APIs for cellular data module. 6 7**File to include**: <telephony/core_service/telephony_radio.h> 8 9**Library**: libtelephony_data.so 10 11**System capability**: SystemCapability.Telephony.CellularData 12 13**Since**: 13 14 15**Related module**: [Telephony](capi-telephony.md) 16 17 18## Summary 19 20### Functions 21 22| Name| Description| 23| -- | -- | 24| [int32_t OH_Telephony_GetDefaultCellularDataSlotId(void)](#oh_telephony_getdefaultcellulardataslotid) | Obtains the default SIM card used for mobile data.| 25 26## Function Description 27 28### OH_Telephony_GetDefaultCellularDataSlotId() 29 30``` 31int32_t OH_Telephony_GetDefaultCellularDataSlotId(void) 32``` 33 34**Description** 35 36Obtains the default SIM card used for mobile data. 37 38**System capability**: SystemCapability.Telephony.CellularData 39 40**Since**: 13 41 42**Returns** 43 44| Type| Description| 45| -- | -- | 46| int32_t | Default SIM card used for mobile data. The value **0** indicates card slot 1, and the value **1** indicates card slot 2.| 47