A call transfer is a telecommunications mechanism that enables a user to relocate an existing call to another phone or attendant console by using the transfer button and dialing the required location. The transferred call is either announced or unannounced.
If the transferred call is announced, the desired party/extension is notified of the impending transfer. This is typically done by putting the caller on hold and dialing the desired party/extension; they are then notified and, if they choose to accept the call, it is transferred over to them. Other terms commonly used for an announced transfer include attended,consult, full-consult, supervised and conference transfer.
On the other hand, an unannounced transfer is self-explanatory: it is transferred without notifying the desired party/extension of the impending call. It is simply transferred to their line by way of a "transfer" key on the operator's phone or by keying in a string of digits which achieves the same function. Other terms commonly used for an unannounced transfer include unsupervised and blind. Unsupervised call transfer can be either warm or cold - depending on moment when B-leg is disconnected. See also Call forwarding