question

Why is it that sometimes when I transfer a call from my Polycom IP 335 HD phone to an internal extension, the call receiver cannot pick up my call, but can see the call I am transferring on their Polycom VVX500 and can pick it up. In the meantime, I can still hear the hold music and can't tell that the call was picked up. I want to be able to introduce the call prior to it being picked up blindly.