Polycom VVX 500 series - How do I transfer a call if I dont need to talk to the recipient before I send the caller through (Blind transfer)?

End User Training Participant Guide
Polycom VVX 500 and 600 Series Phones
8
Holding Calls
How do I place a caller on hold?
When you are on an active call, tap the Hold soft key.
Notes
How do I take a caller off hold?
When a caller is on hold, you see a Resume soft key. Tap it to return to the caller
on hold.
If you have two callers on hold, or are on an active call and have a caller on
hold, tap the onscreen caller ID for the call to which you would like to
return, then tap Resume.