The sendTones() method of the Telephony Interface generates multiple DTMF tones, with a specified duration for each tone, and an optional delay before generation starts. The tones are sent to the currently active call.
The startTone() method of the Telephony Interface begins generating the tone for the specified DTMF character. The tone is sent to the currently active call, and continues to sound until a corresponding call to Telephony.stopTone().
The add() method of the DataStore interface adds a new record to the data store; if the record you are attempting to add already exists, it will throw an exception.
The onchange event handler of the DataStore interface fires when a change is made to the data store. Its main use is to synchronize different apps that are using the data store when a change is made. When fired, this event returns a DataStoreChangeEvent, which can be used to handle the change that was just made. Alternatively, when the event fires you could create a DataStoreCursor and iterate through all the records, if needed.