I still service half a dozen ZTDs, a couple ZTSs and a smattering of Omegas IIIs and IVs. They did in fact use the wht/or pair for T/R audio, with the wht/bl used as a bypass pair and wht/gn for DC voltage. I even have a 412 and one solitary 128, which I am proud to say, was recently converted from coal to regular house current.
Wow - you've got more vintage systems than we do! I'll admit I don't know what the 128 is. We did an inventory earlier this year and don't recall coming across 128 parts and phones. I'll ask if we ever had any. In 2018 we replaced an Omega III with an Adix.
I have a modified 1A2 system at home. I've replaced 400E lines cards with my own circuits so standard non-1A2 phones can initiate off hook lamps and hold. One of the IDFs is a 66 block behind the living room couch. The system was handy when everyone was living here - at dinnertime pressed 0 on the intercom to page throughout the house.
Next time the customer runs into the trouble of not being able to connect I'll keep re-installing the Icon Programmer in mind. I'll see if it could be installed on a second PC. This particular system was not installed by us. It was offered to us to service after another company took it over but had no Iwatsu experience.
For a couple months I've had a 5910 at home connected to our office system, and a Grandstream phone to our hosted system. The 5900 is a great IP phone IMO. Actually I think most Iwatsu phones/systems were. We sent several 5900 series phones out to customer's homes with POE adapters in the last few months that were fortunate to have an ECS with an MBU.
