Press the CONF. button.

Call the third party either internal or external.

 (Internal) If another extension, dial the extension 

  (External) If an outside party, dial 0 or select another line, dial the number

Press the CONF. button.  Conference is established.

To terminate one party and talk to the other.

Press the CO Line key or Intercom key of the party you want to remain connected.  

The other party is disconnected (terminated)

To establish an unattended conference.

While having a conversation with two outside parties;

Press the CONF. key to leave the conference. 

The other two people remain connected.

Press the flashing CO Line key to rejoin the conference.

By default programming, an unattended conference can only last 3 minutes.  This time can be extended in the Panasonic system programming.

Press the Flash key

The other party is placed on hold.

Call the second party, either outside or internal (dial 0 and the new number if an outside call or dial the intercom number if an internal call).

After the second party answers.

Press the Flash key

Dial 3

Conference Call is now established.

If you hang up, all parties are disconnected.