I am assuming all CICS require a single pair cross-connect to extensions?

The extensions seem to be showing proper signs of life except the audio is missing - no DT for ICM and CO, & no sound of battery open circuit. Audio does work to extension because when a line button is selected there is a 5 second delay, then the display shows 'no service' and a busy signal is produced on the speaker.

I will go back onsite this PM to temp. bypass PBX with 4 line phones

Thank you for help

You only need to know the right button to push-