Device Identifier Types
The fax service can maintain two device IDs for each fax device.
When communicating with virtual fax service providers (FSPs) and routing extensions, the fax service uses a logical device ID. A logical device ID is generated by the fax service for each Telephony Application Programming Interface (TAPI) device and virtual FSP device.
The second ID is the TAPI permanent line ID of the device. When communicating with a TAPI FSP, the fax service uses the device's TAPI permanent line ID.
An extension that is passing a device ID to the extension configuration interface must specify the device ID type to allow the service to access the correct device based on the ID provided. The extension must do this when it calls the FaxExtGetData, FaxExtRegisterForEvents, and FaxExtSetData functions.
The following device ID types are defined for use by extensions.
| Value | Meaning | Extension Type |
|---|---|---|
| DEV_ID_SRC_FAX (Logical Device ID) |
Specifies a device ID generated by the fax service or by a virtual FSP. Fax routing extensions and virtual FSPs should use this value. | Virtual FSPs and routing extensions |
| DEV_ID_SRC_TAPI (TAPI Permanent Device ID) |
Specifies a device ID generated by a TAPItelephony service provider (TSP). FSPs that are TAPI-based should use this value. | TAPI FSP |
The fax service ensures the uniqueness of virtual device IDs and of the internal device IDs that it generates. However, it is possible (although unlikely) that a TAPI device ID could conflict with another TAPI device ID because TAPI 2.x does not require that TSPs provide permanently unique device IDs.
For more information about the special device identifier zero (ID = 0), see Storing Global Configuration Data.