To transfer a call, we press the 'Trans' key, dial the desired number and wait for response. Once we get a response, we press the 'Trans' key again to complete transfer. If we get a busy tone from the called end or due to any reason the transfer can not be completed, the DN key (next to which a telephone icon goes on blinking till the transfer is completed) is to be pressed lightly. This will lead to cancelation of the tansfer action and return us to the first party. I think, the 'Swap' key is specific to particular models of Nortel phones.