Newer Phones: [FCN] 704059. [SEND] and [END] keys select options. To monitor calls, [SEND], volume keys to select channel number, then # key. To exit, enter *99**
on Older phones, press and hold FCN & enter 987 STO to edit, END to exit.
To use the back door test mode, available even when the phone is locked, Press and hold FCN and enter 923885. Another test mode is FCN 904059.