Failing to configure my VOIP phone on my NEC PABX. it started to bother me after changing fault IP phone to put a new phone. can someone help i need to bring back the once working VOIP extension.

SOURCE: How do I change someone's name for a specific extension?

input pasword

SOURCE: Interconecting 2 Panasonic KX-TDA 200 & KX-TDA600

You are asking for some very advanced setup features, as far as connecting them you need the IPGateway cards. They are cat5 cards that will do the trick. However programming the setup to do what you want will be VERY time consuming and not to easy to walk someone through. On-site tech is highly recommended for that much programming and work.

SOURCE: Change Extensions on NEC IDK Phone?

It is easier to move the wires but if you know how to go into programming than change the extension numbers on the ports in mb 4-10

SOURCE: i am unable to push the configuration files into polycom soundpoint ip 330 through tftpd

This means the phone's SIP application has been erased. You will need to download the SIP app and BootROM from the Polycom support page, host the files on a boot server, and then point the phone to this server from the server menu so the phone will reboot and download the files.

http://www.polycom.com/support/voice/soundpoint_ip/soundpoint_ip330_320.html

SOURCE: How do i reset philips voip4332b ip phone base unit to company default.

This should solve your problem:

1. On your phone select: Menu > System > Base Select

Select "Auto" and press "ok"

2. On your phone select: Menu > System > Register 
(you might be prompted to enter a PIN if so the default is "0000" )

3. On the base station press and hold down the  "Page" button for 4-5 secs until the green light starts to blink. At this point the phone should be now able to find the base station.