There is no option for conference calling

You will need to configure this through whatever SIP gateway you are using, it is not configured through the handset.

This is configured fromt he backend system. Ask you admin.

what are you trying to connect this to? cme

How to set a Cisco IP phone to factory default Reset configuration of Cisco IP Phone (7910, 1911, 7940, 7941, 7960, 7961)

To set the Cisco IP phone to factory default completes the following steps: should be completed:

For 7940, 7941, 7960, 7961 phones:

1. Power up the phone (unplug power cable and plug in again and hold the # key.
2. Release # when lights start flashing.
3. Press 123456789*0#.
4. Press 1 to keep network configuration or 2 to lose the network configuration.

For 7906G and 7911G phones:
1. Power up the phone (unplug power cable and plug in again and hold the # key.
2. Release # when MWI starts flashing.
3. Press 3491672850*#.

You would need either a call manager or call manager express to configure the phone and connect to the phone line.

I would check the firmware on the phones. Also, check that your switches are properly configured. Duplex settings do matter. If your using cisco switches; do a "show interface" and check for CRC errors etc.

Here are the instructions for configuring these units for 3cx

http://www.3cx.com/sip-phones/cisco-7940.html

http://www.3cx.com/sip-phones/polycom-soundpoint.html

Since the 3cx softphone worked well, I don't see why you couldn't configure each as for 3cx and make them work as well.

It sounds like you have enabled Do No Disturb accidently. This can be turned on and off by pressing the DND softkey button along the bottom of the LCD display. You might need to press the 'more' softkey to display all options.

No most system are maxed on the phone ... but if you had a panasonic system they are know for multi conferencing.

This phone can be access through a menu/ setting buttons.

Useful link on how to navigate through the phone:
http://www.cisco.com/warp/public/779/largeent/avvid/products/7940/7940_topic3.htm
I think the main problem is to determine the intergrated router or Call manager configuration
You can also connect on switch and type:show cpd neighbor This will show the physical port connections