Used 7940 stuck on Protocol Application Invalid

[Callan hill]

I got this phone off a work friend because it wouldn’t work in his home network. When I bought a power cable and Ethernet and then powered it on it’s stuck in the Protocol Application Invalid screen and I do not own CUCM. I rely on the 3PCC Versions of the phones, so I have no idea how to fix this issue. Someone help?

[Maren Mahoney]

The Cisco 7940 phone does have an old firmware that allows it to run as a 3rd-party SIP endpoint (not 3PCC). However, the phone has been End of Life for so long, I doubt the firmware is available anywhere. If you don't have CUCM/CUCM Express or Asterisk (which can run SCCP phones) you may be out of luck.

Maren

[Callan hill]

So then how would I get rid of Protocol Application Invalid screen?

[Maren Mahoney]

Use the Settings menu to determine what firmware it is running in the off chance it's already running SIP (unlikely - the screen would say so). It is a bug and it seems a factory reset won't fix it.

I've not run into this issue myself, so I used "Teh Google" and came up with a few things....

https://community.cisco.com/t5/ip-telephony-and-phones/cisco-7940-protocol-application-invalid/td-p/2996580 

https://community.cisco.com/t5/ip-telephony-and-phones/7960-stuck-protocol-application-invalid/td-p/2096891 

https://community.cisco.com/t5/other-collaboration-subjects/cisco-7940-ip-phone-problem-protocol-application-invalid/td-p/584542 

You'll need to parse the docs to fit your own network and situation, but it does look like the phone is recoverable. Let us know if you have questions.

Maren

[Callan hill]

Hey Maren,

This phone is not being used in a work environment so all these answer to not help me. It is connected to a switch from my home network. Like I just powered it in and it showed the Protocol Application Invalid screen. So I do not know how I can fix this.

[Maren Mahoney · Accepted solution]

Unfortunately, this phone is not designed to work outside of a Cisco Collaboration environment unless it is running the SIP firmware (and with that firmware it is a *very* basic SIP phone). The fix for the bug you encountered is listed in the links I provided. If that is not possible in your environment you may not be able to use the phone.

I wish I had a better answer for you, but that's what there is. It is possible that someone else here has a solution for you.

Maren

[Leo Laohoo]

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@Callan hill wrote:
So then how would I get rid of Protocol Application Invalid screen?

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Factory reset the phone and erase the CTL.  

[Callan hill]

So how would I erase the CTL? (Sorry I am very new to VOIP phones)

[Maren Mahoney]

A factory reset will erase the CTL as part of the reset. It will delete all information, returning the phone to an 'out of the box' status. Certainly give it a try, but the other folks have written that a factory reset does not resolve the issue you are facing. Doing a factory reset certainly won't hurt, though.

That said, if the phone is currently running the SIP firmware that firmware will be deleted during a factory reset. The phone will return to the SCCP factory firmware stored in the phone.

Maren