Yealink SIP-T48G Administrator's Guide

Appendix
851
Step
Action
Description
F7
ACK—User A to Proxy Server
User A sends a SIP ACK to the proxy
server, The ACK confirms that User A
has received the 200 OK response. The
call session is now active.
F8
ACK—Proxy Server to User B
The proxy server sends the SIP ACK to
User B. The ACK confirms that the proxy
server has received the 200 OK
response. The call session is now active.
F9
INVITE—User C to Proxy
Server
User C sends a SIP INVITE message to
the proxy server. The INVITE request is
an invitation to User A to participate in
a call session.
In the INVITE request:
 The IP address of User A is inserted
in the Request-URI field.
 User C 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 C is
ready to receive is specified.
 The port on which User A is
prepared to receive the RTP data is
specified.
F10
INVITE—Proxy Server to User
A
The proxy server maps the SIP URI in the
To field to User A. The proxy server
sends the INVITE message to User A.
F11
180 Ringing—User A to Proxy
Server
User A sends a SIP 180 Ringing
response to the proxy server. The 180
Ringing response indicates that the user
is being alerted.
F12
180 Ringing—Proxy Server to
User C
The proxy server forwards the 180
Ringing response to User C. User C
hears the ring-back tone indicating that
User A is being alerted.

Yealink SIP-T48G Specifications

General

Expansion module support	Yes
Handset type	Wired handset
Product type	IP Phone
Product color	Black
Volume control	-
Display diagonal	7 \
Display resolution	800 x 480 pixels
Lines quantity	- lines
Phonebook capacity	1000 entries
Number of VoIP accounts	6
AC adapter input voltage	100 - 240 V
Number of handles included	1 pc(s)

Weight and Dimensions

Width	266 mm
Height	185 mm