19.4.7 H.450 Call Hold, Transfer and Forward Mode Gateway provides H.450 function including call hold, transfer and forward. Please be noted that both calling and called site have to support H.450 feature. For call forward function, it only works under Proxy mode. Of course, Proxy must support H.450 feature. It is better for user to prepare a telephone set supported [FLASH] function on keypad. If telephone set does not support [FLASH] function on keypad, user is possible to click the Hook quickly by sending FLASH message. The default FLASH value for Gateway is between 100ms to 300 ms. It is said the value of Gateway is subject to the telephone set. �� Call Hold press [FLASH] By pressing the FLASH after making a call, both site shall hear the 2nd dial tone generated by Gateway. To retrieve the call back, just press the FLASH again. �� Call Transfer press [FLASH], then [transferring number] For example, A call B, B transfer to C A make call to B, B press FLASH. A and B hear 2nd dial tone. B presses the Cs number. C ringing and A hear the RingBack tone. B Hang up its call. A and C Make call.