ISDN cable

My NT1 device in the junk pile has 3 jacks, but they all go to different things? Not to the wall?

One is simply for power. One is input, and one is output. You'll have to really designate what your 3 jacks do? Are they like mine? Or do you have a three input NT1 for 3 different BRI U lines?

Typically, your NT1 would take an ISDN U signal, which comes in on the center pair of a USOC jack, and breaks it out to an S/T bus which plugs into your ISDN device. The S/T bus is either 2 pair or 4 pair depending on your power bus and power requirements.

I think you are putting too much thought into this, what are you really trying to do? Can't the NT1 just sit right next to the video conferencing unit? What do the 3 jacks do?

Back when we used ISDN for our videoconferencing, I made up an adapter to do this. I used four port surface mount box and four RJ-45 jacks. Each of the pairs is punched down the the white-blue pair of the jacks on the left. See above.

We then got rid of all our ISDN stuff and now the VC goes over the IP backbone (we have Cisco switches, etc).

Picturetel used three separate RJ-45 jacks for three BRI lines, each having two 'B' phone numbers. Total data rate was 384kbps. Nowadays people often change to a DSL line to save money.