Remove the IC button completely from the phone. Just use Call Keys. When you are on the phone, outside trunk OR intercom, and you receive another call on intercom level, you will see your next available call key flash. The caller will hear a busy signal, but if they can be made accustomed to waiting, they will get answered, if you choose to answer them. Just make sure that your system forwarding is not set to forward on busy for intercom calls.
One word of caution:When a phone is programmed with an IC key, pressing a Call key is the same as pressing outgoing, and the dial tone you hear is either ARS or Trunk dialtone. When you take the IC key out of the keymap, pressing the call key only gives you intercom dial tone, and you must press either the Outgoing key, or dial the Outgoing access code to start a call for outside the office.
