lineGenerateTone function (tapi.h)

Article
10/05/2021

The lineGenerateTone function generates the specified inband tone over the specified call. Invoking this function with a zero for dwToneMode aborts the tone generation currently in progress on the specified call. Invoking lineGenerateTone or lineGenerateDigits while tone generation is in progress aborts the current tone generation or digit generation and initiates the generation of the newly specified tone or digits.

Syntax

LONG lineGenerateTone(
  HCALL                    hCall,
  DWORD                    dwToneMode,
  DWORD                    dwDuration,
  DWORD                    dwNumTones,
  LPLINEGENERATETONE const lpTones
);

Parameters

hCall

Handle to the call on which a tone is to be generated. The application must be an owner of the call. The call state of hCall can be any state.

dwToneMode

Defines the tone to be generated. Tones can be either standard or custom. A custom tone is composed of a set of arbitrary frequencies. A small number of standard tones are predefined. The duration of the tone is specified with dwDuration for both standard and custom tones. The dwToneMode parameter can only have one bit set. If no bits are set (the value 0 is passed), tone generation is canceled. This parameter uses one of the LINETONEMODE_ Constants.

dwDuration

Duration in milliseconds during which the tone should be sustained. A value of 0 for dwDuration uses a default duration for the specified tone. Default values are:

CUSTOM: The tone is sustained until it is shut off, usually by user interaction or an equipment time-out.

RINGBACK: The tone is sustained until it is shut off, usually by user interaction or an equipment time-out.

BUSY: The tone is sustained until it is shut off, usually by user interaction or an equipment time-out.

BEEP: The tone is sustained until it is shut off, usually by user interaction or an equipment time-out.

BILLING: Fixed (single cycle).

dwNumTones

Number of entries in the lpTones array. This parameter is ignored if dwToneMode is not equal to CUSTOM.

lpTones

Pointer to a LINEGENERATETONE array that specifies the tone's components. This parameter is ignored for standard LINETONEMODE_ Constants tones such as LINETONEMODE_BUSY. If lpTones is a multifrequency tone, the various tones are played simultaneously.

Return value

Returns zero if the request succeeds or a negative error number if an error occurs. Possible return values are:

LINEERR_INVALCALLHANDLE, LINEERR_NOTOWNER, LINEERR_INVALCALLSTATE, LINEERR_OPERATIONUNAVAIL, LINEERR_INVALPOINTER, LINEERR_OPERATIONFAILED, LINEERR_INVALTONEMODE, LINEERR_RESOURCEUNAVAIL, LINEERR_INVALTONE, LINEERR_UNINITIALIZED, LINEERR_NOMEM.

Remarks

The lineGenerateTone function is considered to have completed successfully when the tone generation has been successfully initiated, not when the generation of the tone is finished. The function allows the inband generation of several predefined tones, such as ringback, busy tones, and beep. It also allows for the fabrication of custom tones by specifying their component frequencies, cadence, and volume. Because these tones are generated as inband tones, the call would typically have to be in the connected state for tone generation to be effective. When the generation of the tone is complete, or when tone generation is canceled, a LINE_GENERATE message is sent to the application.

Only one inband generation request (tone generation or digit generation) is allowed to be in progress per call across all applications that are owners of the call. This implies that if tone generation is currently in progress on a call, invoking lineGenerateDigits cancels the tone generation.

If the LINEERR_INVALPOINTER error value is returned, the specified lpTones parameter is invalid or the value specified by the dwNumTones parameter is too large.

Requirements

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