Call Accept, Reject, and Redirect

In environments like ISDN, call offering is separate from alerting. On an ISDN network, call offering is the process of sending a call-setup message from the switch. This occurs before ringing, so the call can be redirected before it is answered. The lineAccept function means "start ringing" for ISDN. For POTS, it means that some application has accepted responsibility for the call and has presented it to the user.

After a call has been offered to tapi32.dll, a time window exists during which tapi32.dll has a number of options:

• tapi32.dll can simply answer the call using TSPI_lineAnswer.
• tapi32.dll can accept the call using TSPI_lineAccept, which also initiates alerting to the caller (as ringback), and to the called party (as ring).
• tapi32.dll can reject the offering call using TSPI_lineDrop. The call remains valid but transitions to the idle state.
• tapi32.dll can redirect the call using TSPI_lineRedirect, which deflects the offering call to another address. The call remains valid but transitions to the idle state.