Possible cause:

The station number is incorrect. 

Possible response:

Enter a correct station number. 

Possible cause:

You tried to activate a disabled function. 

Possible response:

Ask the service personnel to authorize you to use the function. 

Possible cause:

The station number you dialed does not exist. The telephone you are trying to call is unplugged. 

Possible response:

Enter a correct station number. Try calling the telephone again later on. 

Possible cause:

You dialed your own station number.  

Possible response:

Enter a correct station number. 

Possible cause:

All memory locations for external station numbers are currently in use. 

Possible response:

Try again later on. 

Restart the Telephone

Other errors (e.g. the display shows "System forced logoff") can be repaired sometimes by restarting the telephone. 

Press the keys simultaneously and follow further prompting.