This function toggles speakerphone on/off while in a phone call.

DWORD ToggleSpeakerphone(void);

Parameters
none

Return values
Zero indicates success. A non zero number indicates that an error occurred. For additional error information, enable the library debug mode.

Remarks
This function checks the OS version, if the major version is 4 or less, it will control the Speakerphone by using direct Audio Driver messages. For OS version greater then 4, it will controll the Speakerphone by using ossvcs.dll exports 217 and 218. For more details see: Speakerphone Article

Requirements
OS Versions: Windows CE 1.0 and later.
Header: dynril.h.
Dll Library: dynrildll.dll.