Some phone sets support the capability of downloading data from or uploading data to the phone device, which allows the phone set to be programmed in a variety of ways. Win32 Telephony models these phone sets as having one or more download or upload areas. Each area is identified by a number that ranges from zero to the number of data areas available on the phone minus one. Sizes of each area can vary. The format of the data itself is device specific.
The TSPI_phoneSetData function downloads a buffer of data to a given data area in the phone device. TSPI_phoneGetData uploads the contents of a given data area in the phone device to a buffer.
When a data area of a phone device is changed, the service provider sends a PHONE_STATUS message to the tapi32.dll callback function to notify it about the state change. Parameters to this message provide an indication of the change.