There are 3 ways to transfer a call: blind transfer, semi-attended transfer, and attended transfer.  

Blind Transfers

Direct transfer to another extension without initiating a call to the end destination.

Semi-Attended Transfers

Transfer the call when the target phone is still ringing.

Attended Transfers

Transfer the call after the 2nd party answers.

The following instructions detail how to transfer a call on a Yealink T21P phone.

You can transfer a call in the following ways:

Blind Transfer

1. Press the TRAN button or the Tran soft key during a call. The call is placed on hold.
2. Enter the number you want to transfer to.
3. Press the TRAN button or the Tran soft key.

Semi-Attended Transfer

1. Press the TRAN button or the Tran soft key during a call. The call is placed on hold.
2. Enter the number you want to transfer to and then press the #SEND key.
3. Press the TRAN button or the Tran soft key when you hear the ring-back tone.

Attended Transfer

1. Press the TRAN button or the Tran soft key during a call. The call is placed on hold.
2. Enter the number you want to transfer to and then press the #SEND key.
3. Press the TRAN button or the Tran soft key when the second party answers.