Linksys SPA921-NA Administrator's Manual page 124

Regional Tab
Media Loopback Code
Referral Services Codes
Linksys 900 Series IP Phone Administrator Guide
5-26
The star code used for enabling media loopback on the phone.
The default is *03.
These codes tell the 900 Series phone what to do when the user places the current
call on hold and is listening to the second dial tone.
One or more *code can be configured into this parameter, such as *98, or
*97|*98|*123, and so forth. Max total length is 79 chars. This parameter applies
when the user places the current call on hold (by Hook Flash) and is listening to
second dial tone. Each *code (and the following valid target number according to
current dial plan) entered on the second dial-tone triggers the 900 Series phone to
perform a blind transfer to a target number that is prepended by the service *code.
For example, after the user dials *98, the 900 Series phone plays a special dial
tone called the Prompt Tone while waiting for the user the enter a target number
(which is checked according to dial plan as in normal dialing). When a complete
number is entered, the 900 Series phone sends a blind REFER to the holding party
with the Refer-To target equals to *98<target_number>. This feature allows the
900 Series phone to hand off a call to an application server to perform further
processing, such as call park.
The *codes should not conflict with any of the other vertical service codes
internally processed by the 900 Series phone. You can empty the corresponding
*code that you do not want to 900 Series phone to process.
Chapter 5 SPA900 Series Phone Field Reference
Document Version 3.0