Yealink T27P Administrator's Guide

Administrator’s Guide for SIP-T2_Series_T4_Series IP Phones
578
Step
Action
Description
F1
INVITE—User A to Proxy
Server
User A sends an INVITE message to a
proxy server. The INVITE request is an
invitation to User B to participate in a
call session.
In the INVITE request:
 The IP address of User B is
inserted in the Request-URI
field.
 User A is identified as the
call session initiator in the
From field.
 A unique numeric identifier
is assigned to the call and
is inserted in the Call-ID
field.
 The transaction number
within a single call leg is
identified in the CSeq
field.
 The media capability User
A is ready to receive is
specified.
 The port on which User B is
prepared to receive the
RTP data is specified.
F2
INVITE—Proxy Server to User
B
The proxy server maps the SIP URI in the
To field to User B. The proxy server
sends the INVITE message to User B.
F3
180 Ringing—User B to Proxy
Server
User B sends a SIP 180 Ringing response
to the proxy server. The 180 Ringing
response indicates that the user is being
alerted.
F4
180 Ringing—Proxy Server to
User A
The proxy server forwards the 180
Ringing response to User A. User A
hears the ring-back tone indicating that
User B is being alerted.
F5
200 OK—User B to Proxy
Server
User B sends a SIP 200 OK response to
the proxy server. The 200 OK response
notifies the proxy server that the

Yealink T27P Specifications

General

Wall Mountable	Yes
Local Phonebook	1000 entries
Bluetooth	No
Wi-Fi	No
Gigabit Ethernet	No
Display	3.66" 240x120 pixel graphical LCD with backlight
Audio Features	HD voice, Full-duplex speakerphone
Network	Dual-port 10/100 Ethernet switch
Protocols	SIP v1 (RFC2543), v2 (RFC3261)
Power	IEEE 802.3af PoE
Connectivity	2 x RJ45 10/100M Ethernet ports
Voice Codecs	G.711(A/μ), G.722, G.723, G.729AB, G.726
EHS	Supports EHS with Plantronics headsets
Headset Port	Yes
Power Adapter	5V DC (optional)