Sony HIPATH 500 - Manual (Page 53)

Enhanced phone functions
53
Step by step
Send trunk flash (not for HiPath 500)
To activate ISDN-type services and features through the
network carrier’s analog trunks or those of other com-
munications platforms (such as "consultation hold"), you
must send a signal to the trunks before dialing the ser-
vice code or telephone number.
Prerequisite: You have set up an external connection.
N
Press the key shown.
Select and confirm the option shown.
j
Enter the service code and/or telephone number.
*51=Trunk flash?