Cisco IP Phone How To Reset To Factory Settings Instructions CP 9971, 8800, 8900, 8845, 8851, 8841, 8831, 7961, 7960, 7945, 7942, 7941, 7940.

This would be crucial especially if the phone is hardened, not being able to reset or change settings could prevent a phone registering in a new environment or even when migrating from office to office. This applies even if you are trying to migrate the phone to another platform such as Asterisk/FreePBX etc...

This guide applies to nearly all of the Cisco IP phones that you would use in CME or CUCM from several years ago including models: 9900, 9971, 8800, 8900, 8845, 8851, 8841, 8831, 7961, 7960, 7945, 7942, 7941, 7940.

Updated Guide

1.) Reboot phone and hold the "#" key.

2.) Once the headset and volume key are green release the "#" key.

3.) Immediately press 123456789*0# (if you are successful when you press 1 the headset button should go dark). If it doesn't try again. Timing is key and being off by .25 seconds is too much.

Here is Cisco's guide (timing is everything and it is more tricky than trying to jail break your iPhone):

Step 1 -- While powering up the phone, press and hold #.

Step 2 -- When the light on the mute button and handset light strip turns off and all other lights (line button, headset button, speakerphone button and select button) stay green, press 123456789*0# in sequence.

When you press 1, the lights on the line buttons turn red. The light on the select button flash when a button is pressed.

If you press the buttons out of sequence, the lights on the line button, headset button, speakerphone button, and select button turn green. You will need to start over and press 123456789*0# in sequence again.

After you press these buttons, the phone goes through the factory reset process.

Do not power down the phone until it completes the factory reset process, and the main screen appears.

Here is an alternative description some have had better luck with:

Step 1	Unplug the phone: If using PoE, unplug the LAN cable. If using the power cube, unplug the power cube.
Step 2	Wait 5 seconds.
Step 3	Press and hold # and plug the phone back in.
Step 4	When the light on the Mute button and handset light strip turns off and all other lights (Line button, Headset button, Speakerphone button, and Select button) stay green, press 1234567890# in sequence. When you press 1, the lights on the line buttons turn red. The light on the Select button flashes when a button is pressed. If you press the buttons out of sequence, the lights on the line button, headset button, speakerphone button, and Select button turn green. You need to start over and press 1234567890# in sequence again. After you press these buttons, the phone goes through the factory reset process.