To give a little history. The EK-612 is the only piece I have. I have no phone extentions. It was removed from an office we moved into (Sound Company I worked for in 1991) when we moved from our old location and into the new one we brought and installed our AT&T phone system. The EK-612 was in crawl space and wired but no extentions remained in any of the offices. The installer did not want it, nor did my boss, so I brought it home. I have had it in storage for several years after tinkering with it initally. A friend and I are soon to open a Hammond Organ retail store. We will be the only authorized Hammond-Suzuki in Los Angeles, and I was hoping to use this with the purchase of roughly 3 delphi (or equivilant)phone terminals to set up a nice reliable and basic phone system in our new office. I also have the System Practice 01400IMG EK-612 Installation and Maintenance Manual in original print which I purchased from TIE/Nitsuko around 1994. This explains why I do not have a phone extention for testing. With the unit plugged and after the software loads and the relays click, applying a ring signal to CO jacks 2,3, and 4 will cause the ring relay inside the unit to cycle. Applying a ring signal to CO jacks 1,5, and 6 produce nothing. Can I still assume that it is just a matter of programming? I am also curious to know if I should replace the 3 cell memory retention battery, since it is obviously so old circa 1984, though there are no signs of leakage or corrosion, better safe than sorry. I am handy with a soldering iron, it is what I do for a living, fix Hammond organs and at times computer circuitry which can be difficult on one's eyes as well as nerves in some of the first digital carillon clock systems.