Press Trans/Conf
or 
.
Dial the Trunk Single Flash or Trunk Double Flash Feature Access code.
Wait for dial tone.
Dial the Centrex feature access code.
Trunk Flash lets you single or double flash a trunk to request Centrex features.
TIP: Once a user receives dial tone from the CO (after flashing a trunk), the system cannot restrict dialing.
Trunk Flash is supported for the following types of trunks:
LS/GS CO
E&M
T1 DID/TIE
T1 E&M
T1 CO
For analog trunks:
Trunk Flash is supported for both LS and GS trunks on the LS/GS trunk card.
Trunk Flash is supported for LS trunks on all other analog trunk interfaces in the MiVoice Business system.
MSDN or DASSII trunks do not support Trunk Flash.
DISA callers cannot use Trunk Flash.
To initiate this feature, you must be in talking state on the trunk that is to be flashed with no one on Consultation Hold. You cannot initiate the feature if you are in a conference unless the conference uses the far end's conference capabilities.
A Symbol Wireless phones cannot initiate this feature.
Enter the duration of the single trunk flash or each of the flashes for a double trunk flash in the Flash Timer field of the appropriate Trunk Circuit Descriptor form. For a double flash, the time between flashes is hard-coded at one second.
Enable Trunk Flash Allowed for both the telephone that will perform the flash and the trunk that will be flashed.
Feature
Access Codes form
If you intend to use a feature access code in Operation, assign the Trunk Double Flash and Trunk Single Flash codes
Multiline
Set Keys form
If you intend to use a feature key in Operation, program a Single Flash and a Double Flash key or use Superkey (see Feature Keys for more information on Superkey programming).
You can insert a Trunk Flash into a System Speed Call by using the flash character ( f or F). You can insert a Trunk Flash into a Personal Speed Call or Speed Call Key by using the Flash key, Trans/Conf key, or Insert Flash softkey. Note that you cannot program a flash into a Speed Call Key in the programming forms.
NOTE: When programming Speed Call on 5320/5320e, 5330/5330e, 5340/5340e IP Phones, pressing quickly the '#' button twice, inserts the flash character (F).
Supported on all devices.
To flash a trunk:
Dial the Trunk Single Flash or Trunk Double Flash Feature Access code.
To flash a trunk:
Press the Flash - Single or Flash - Double feature key.
To flash a trunk while on an outside call:
Press Trans/Conf
or .
Dial the Trunk Single Flash or Trunk Double Flash Feature Access code.
Wait for dial tone.
Dial the Centrex feature access code.
To flash a trunk:
Press 
.
Dial the Trunk Single Flash or Trunk Double Flash Feature Access code.
Wait for dial tone.
Dial the Centrex feature access code.
To flash a trunk:
Press FCN then press 1.
Dial the Trunk Single Flash or Trunk Double Flash Feature Access code.
Wait for dial tone.
Dial the Centrex feature access code.