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Help with uc540 config

I have the following scenario to config & install:

UC540 w/3 SPA504 phones directly connected, 1 SPA525 phone connected via ssl vpn

Initially:  AT&T will supply 4 fxo lines

In a month: service will change to AT&T FlexReach SIP trunks

Customer currently has a key-system setup; they want to continue to be able to see incoming calls on all phones

What is the best way to set this up?  Do I understand correctly that key-system on the UC540 will not work with SIP trunks?


From your post it sounds like you want all inbound calls to ring all available extensions. If this is correct you can achieve this by setting up your inbound calls to ring a blast group that has all extensions as members.

CCA 2.2.1 HELP under Voice System Settings:

Voice System Type

Choose a voice system type, either PBX or  Keysystem.

When you choose Keysystem, the system is  placed in a hybrid mode, where SIP trunks are  treated as PBX lines, and local trunks (FXO, BRI, PRI)  are treated as key system lines. In this mode:

  • FXO trunks and T1/E1 CAS trunks are  configured as direct trunk lines.
  • Permissions are not set on key system lines.  All calls from these direct trunk lines are  unrestricted.

I also agree with the Blast Group comment.  In PBX mode, you can set up a bast group to alert all phones when an ingress FXO or SIP trunk call comes in.

The thing about KEY SYSTEM mode, is you cant toggle to it.   You would have to factory reset to toggle between PBX and it (and visa versa).
In fact, most deployments use PBX mode and use the BLF (Monitor and watch and share) buttons to monitor and interact among phones.

Steve DiStefano
Systems Engineer
U.S. Field Channel Sales team

P.S.   Most of Cisco is closed till after new years day.  SBSC and TAC are open during this closure.

Thanks.  It sounds like pbx with blast group is the way to go.  I was thinking that in pbx mode it had to go through the autoattendant, but I guess that's not required.

AA is optional.   SIP Trunk DIDs or FXOs can be directed to any number you want.