lineDial function (tapi.h)

The lineDial function dials the specified dialable number on the specified call.


LONG lineDial(
  HCALL  hCall,
  LPCSTR lpszDestAddress,
  DWORD  dwCountryCode



Handle to the call on which a number is to be dialed. The application must be an owner of the call. The call state of hCall can be any state except idle and disconnected.


Destination to be dialed using the standard dialable number format.


Country or region code of the destination. This is used by the implementation to select the call progress protocols for the destination address. If a value of 0 is specified, a service provider-defined default call progress protocol is used.

Return value

Returns a positive request identifier if the function is completed asynchronously, or a negative error number if an error occurs. The dwParam2 parameter of the corresponding LINE_REPLY message is zero if the function succeeds or it is a negative error number if an error occurs. Possible return values are:



If LINEERR_INVALADDRESS is returned, no dialing has been done. If LINEERR_DIALBILLING, LINEERR_DIALQUIET, LINEERR_DIALDIALTONE, or LINEERR_DIALPROMPT is returned, none of the actions otherwise performed by lineDial have occurred. For example, none of the dialable addresses prior to the offending character has been dialed, no hookswitch state has changed, and so on.

The lineDial function is used for dialing on an existing call appearance. For example, after a call has been set up for transfer or conference, a consultation call is automatically allocated, and the lineDial function would be used to perform the dialing of this consultation call. The lineDial function can be invoked multiple times in the course of multistage dialing, if the line's device capabilities allow it. Also, multiple addresses can be provided in a single dial string separated by CRLF. Service providers that provide inverse multiplexing can establish individual physical calls with each of the addresses and can return a single call handle to the aggregate of all calls to the application. All addresses would use the same country or region code.

Dialing is considered complete after the address has been passed to the service provider; not after the call is finally connected. Service providers that provide inverse multiplexing can allow multiple addresses to be provided at once. The service provider sends LINE_CALLSTATE messages to the application to inform it about the progress of the call. To abort a call attempt while a call is being established, the invoking application should use lineDrop.

An application can set the lpszDestAddress parameter of the lineDial function to the address of an empty string to indicate that dialing is complete, but only if the previous calls to the lineMakeCall and lineDial functions have had the strings specified by lpszDestAddress terminated with semicolons.

The lineDial function can also be used in partial dialing. To initiate a call using partial dialing, the application calls lineMakeCall and specifies a partial dialing string. A partial dial string is any dial string terminated by a semicolon. The call will typically transition to LINECALLSTATE_DIALING after which lineDial can be called to specify more dialing strings, each terminated by a semicolon. Dialing is completed by calling lineDial with a dial string that is not terminated with a semicolon (such as an empty string). This technique allows applications to perform interactive partial dialing with the user or enable more sophisticated dialing than a TSP may be capable of.

If a null destination string, or an empty string terminated with a semicolon (";") is entered in lineMakeCall the application transitions to LINE_CALLSTATE_DIALTONE. The lineDial function can be called in this state to enter a single dial string or multiple partial dial strings, each separated by a semicolon. The application transitions to the LINECALLSTATE_DIALING state after the first digit is entered.

Note  The lineDial function is only available when a call is in LINECALLSTATE_DIALING or LINE_CALLSTATE_DIALTONE. If DTMF is needed while a call is connected (LINECALLSTATE_CONNECTED), use lineGenerateDigits.


Requirement Value
Target Platform Windows
Header tapi.h
Library Tapi32.lib
DLL Tapi32.dll

See also

Basic Telephony Services Reference

Dial Overview

Dialable Addresses



TAPI 2.2 Reference Overview