how to manually d/c Apex system?

I think I mentioned this to your earlier but ...... I'm not familiar with the panel but in most cases, if a panel has been programed to report to central station, it may or may not have telephone line loss detection and/or communication failure notification. So ........... if you don't give it a phone line, it will go into a trouble condition or ............. if you set it off and it can't get through to central it will give you a trouble condition. You'd have to experiment to find out, but if it does have these programed features, you're going to get beeping from the keypad which will have to be reset often and/or you'll have to unpower and power up again, each time.