Convert a bricked Cisco 7940 Phone to SIP protocol


  • Cisco 7940 Telephone with Power supply (or POE port)
  • A Cisco ID with access to software downloads
  • A switch
  • An application that provides TFTP and DHCP services installed on your computer (e.g. TFTpd32)

STEP ONE: Obtain SIP Firmware

WARNING: E-MetroTel has been successful in creating interoperability with the referenced phone with this specific firmware release using our open SIP Standards implementation. E-MetroTel is not responsible for maintaining interoperability support should the manufacturer modify the behavior of their SIP implementation in subsequent releases.

Download SIP software

  • Visit the cisco software download page (
  • Select your product Unified IP Phone 7940G
  • Select the software type Session Initiation Protocol (SIP) Software
  • Select the latest 8.xx software version
  • Download the SIP flash image for non-callmanager or SIP flash image for 3rd party SIP call control environment
  • Extract the downloaded zip file to a new folder and label the folder the same as the software load (e,g. P0S3-8-12-00)
  • The contents extracted will look something like this:

STEP TWO: Prepare Configuration files

There are several configuration files that you will need to prepare: 

  • OS79XX.TXT
  • SIPDefault.cnf
  • SIP(MAC).cnf
  • XMLDefault.cnf.xml

You can download the template files that we have provided at the bottom of this page. Place these files in the same folder as the software files that you extracted above. Change the file extension of the files as follows:

  • SIPDefault.txt to SIPDefault.cnf
  • SIP(MAC).txt to SIP(MAC).cnf
  • XMLDefault.cnf_.txt to XMLDefault.cnf.xml


There is only one line in this file listing the firmware load, make sure the 3rd character in the file is a "S" to represent SIP. For example, the file should look like this:




There are 2 lines in this file you have to check and change if needed. Verify that the image version matches the firmware load you have in the OS79XX.TXT file above and change the Proxy Server address to the IP address of your UCx server.

image_version: "P0S3-8-12-00"

# Proxy Server




The configuration file must be renamed to match the MAC address of your phone exactly. For example, if the MAC address of the phone is "00260B5DCB52", then the file must be renamed to "SIP00260B5DCB52.cnf". (Note the name must be in UPPERCASE.)
Verify the image version matches the firmware load you have in the OS79XX.TXT file.
Replace the tags highlighted in BOLD with the approprate values of the extension that you want configured for the phone.

# SIP Configuration
image_version: P0S3-8-12-00

# Line 1 appearance
line1_name: #EXTENSION

# Identification as it should appear for caller-identification purposes
line1_displayname: #EXTENSIONDISPLAYNAME

# Line 1 Registration Authentication
line1_authname: #EXTENSION

# Line 1 Registration Password
line1_password: #EXTENSIONSECRET

# Text to display on the top right status line of the LCD
phone_label: #EXTENSIONLABEL



Verify that the load information for your phone model matches the firmware load you have in the OS79XX.TXT file.

<loadInformation8 model="IP Phone 7940">P0S3-8-12-00</loadInformation8>  


STEP THREE: Install and configure TFTP Server

  • Download and install TFTpd32 on your computer. 
  • Connect your computer to a switch. (best not to have any other devices connected to the switch)
  • Change the IP address of your computer to with mask
  • Launch TFTpd32 and click on the Settings button.
  • Under GLOBAL tab, select TFTP Server and DHCP Server, deselect all others.
  • Under TFTP tab:
    • Base Directory = Set to directory where the firmware and configuration files are located from STEPS ONE and TWO.
    • TFTP Security = None

  • Under DHCP tab:
    • IP pool start address =
    • Size of pool = 10
    • Def. router (Opt 3) =
    • mask (Opt 1) =
    • Additional Option = 66 and
    • DHCP Settings: Uncheck all boxes except for Bind DHCP to this address

  • Press the OK button and restart TFTpd32.
  • Connect the Cisco IP phone to the same switch as your computer and power it on.
  • The log file will show files being requested and transferred.
  • If all goes well,you will see messages displayed on the phone indicating the new firmware load is being retrieved (wait a few minutes).
  • When the phone comes back up, it should have SIP firmware installed and also provisioned.
  • If unsuccessful, check the log file to troubleshoot and see which configuration file the phone requires and is missing.
Page Tags: