Whistler Pro-58 Settings Help (not in manual)

I just replaced my Bel Vector 960 with the Pro-58.

There are 2 things I found out that are not covered by the menu:

- Press and hold "city" for more than 2 sec, the unit will make a noise, then the numeric indicator will flash. During the flashing, I can press the power button and it will return to normal with 2 beep. What is this for?

- When the unit is off, press Power and Quiet together. The unit can then do a self-start-up test without tone. When the unit finish self-testing, it will end with 1 beep.

What are the other hidden function?