This method generates the specified digits as inband tones using DTMF signaling. Valid digits are 0 through 9, '*', '#', 'A', 'B', 'C', and 'D'. In addition, the comma (,) is also a valid character. A comma injects an extra delay between the signaling of the previous and next digits it separates. The duration of this pause is hardware dependent (usually 500 ms). Multiple commas can be used to inject longer pauses. The exclamation (!) is a valid character. This character causes a "hookflash" operation (one-half second onhook, followed by one-half second offhook before continuing). The application can use GenerateDigits to perform call transfer by generating a sequence of digits that instructs your PBX to transfer a call. Please note that GenerateDigits is an asynchronous operation. GenerateDigits queues the digits to generate and returns immediately. The telephony hardware will start digit generation after the method returns.