Call Transfer allows you to transfer an active call to another 
person, either another extension (for Business phone) or an external 
number.  This can be done either as a Consulted Transfer or a Blind 
Transfer.  
The method to do this is different depending on whether you have an ATA with a standard analog phone or a Polycom Phone.
Desk phones will have a dedicated Transfer key and/or a Transfer soft key when you are on a call. 
 While on the call, hit the Transfer (or Trnsfer or Xfer) button.  You will be 
able to dial the number/extension that you wish to transfer to.  If you 
want to do a Blind Transfer, hit the Blind soft key before dialing the 
second number/extension.  The phones are generally setup to do a blind transfer by default.