Sorry Stewart, I should have posted the problem. The equipment being essentially antiquated, but so rugged (mine has been in service over thirty years it survived a lightening strike about fifteen years ago) I thought that it may not be on anyone's radar.
I lifted the line from the KSU and fed the PSTN port from the demarc. I then connected the Phone port to a single line jack in the system. The single line jacks were installed for trimlines, cordless phones, caller ID boxes, etc. The jacks all have devices that would give A-lead control.
The key sets, original issue WE, lights work off hook, no ring issues due to the ring generator in the KSU. The trimlines off hook cause the lights to work but the cordless does not.
The system will not place the call on hold.
My first thought is that I may need a higher voltage or current level from the Obi.
When I went from copper to fiber the ONT supplied a lower voltage and perhaps lower current so the the single line A-lead devices stopped taking the lines off hold.
I appreciate your thoughts.