The call on hold is temporarily disconnected allowing the application to use the line device for making or answering other calls. Use Unhold()()() to retrieve the held call. Your telephony hardware must support "hard hold" function for Hold method to work. Regular voice modems do not support this function.

Please note that Hold is an asynchronous operation. Hold method instructs telephony system to put the call on hold. When telephony system finishes putting the call on hold, the state of the call changes to TapiCallState.OnHold and CallState event is fired. If the held party hangs up while on hold, the call transitions to the TapiCallState.Disconnected state.