128 Voice API Programming Guide — June 2005
Send and Receive FSK Data
•Implementing Two-Way ADSI Using dx_TxRxIottData( )
10.8.1 Technical Overview of One-Way ADSI Data Transfer
In one-way ADSI data transfer, the ADSI server sends ADSI messages to a CPE device, such as an
ADSI-compliant telephone. The transactions that occur between the server and the CPE during
one-way ADSI data transfer are as follows:
1. The server initiates the data transfer by sending a CPE Alerting Signal (CAS) to the CPE.
2. When the CPE receives the CAS, the device generates an ACK (DTMF ‘A’ signal) to the
server. At this point the CPE device has switched from voice mode to data mode. (If the CPE
device remains in data mode, subsequent transmissions do not require the CAS.)
Note: Only ADSI-compliant CPE devices will respond to the CAS sent by the server. Check
with your manufacturer to verify that your CPE device is a true ADSI-compliant
device. ADSI-compliant devices are also referred to as "Type 3 CPE Devices" by
Telcordia Technologies and the EIA/TIA.
3. Upon receipt of the ACK signal, the server initiates the FSK transmission sequence. Each FSK
transmission sequence can contain anywhere from 1 to 5 messages.
4. The CPE receives the FSK data and uses the checksum included within the sequence to
determine the number of messages successfully received.
5. The CPE device then responds to the server with an acknowledgment digit (DTMF ‘D’)
followed by a DTMF of ‘0’ through ‘5,’ which indicates the number of messages successfully
received.
6. The server interprets the DTMF as follows:
•ACK = ‘D’ followed by a DTMF in the range of 1 – 5
•NAK = ‘D’ followed by a DTMF ‘0’
10.8.2 Implementing One-Way ADSI Using dx_TxIottData( )
The dx_TxIottData( ) function is used to send the CAS to the CPE and implement one-way ADSI
data transfer. To transfer ADSI FSK data, configure the function parameters and structures as
follows:
•Set the wType parameter DT_ADSI.
•Configure the DX_IOTT structure with the appropriate ADSI FSK data file(s). The application
is responsible for constructing the messages and checksums for each transmission.
•Set the termination conditions with the DV_TPT structure.
•Set dwTxDataMode within the ADSI_XFERSTRUC referenced by lpParams to
ADSI_ALERT to generate the CAS.
The following scenario illustrates the function calls that are required to generate an initial CAS to
the CPE and begin one-way ADSI data transfer.
1. Prior to executing dx_TxIottData( ), clear the digit buffer for the desired voice channel using
dx_clrdigbuf( ).