I also have a Exectone CX512 phone system and I am having the same problem and tried to reinitalize but it didn't solve the problem.
I am having a problem trying to program my phone lines to ring at all phones. I am not a programer and I think that is most of my problem. I think I am close but I need someone to review my commands to see why I am not getting the results I expected. The procedure I followed is: (Passsword) (peep heard) FLASH 40 (button 12 lights up) 100107 (peep heard) At this point everything is fine and dandy except for button 10 lighting up in the above buttons. I ignore it and push button 8 for C.O. line. (button lights up and button 10 remains lit). I try to input the following numbers 023 for line 2 to ring day and night but the system will not except even the first number. I have tried unplugging the phone that button 10 corresponse with but no help still the same problem. What am I doing wrong?

Thanks
Josh