Today I got what is now a routine ticket for a MAC-D on a phone. First a little background, unlike some of my luckier geek friends I don't administer a fancy Cisco Unified Call Manager or Avaya IP system. My company's phone system is a
Siemens/Rolm 9751 MOD 80 installed in 1996 and currently maintained by spare parts and good luck. That being said, when a MAC-D comes in, it means working on the 66 Blocks in our MDF and IDFs to make the change instead of just having the user plug the phone into their new office's network jack and being done.
What was unique about today's ticket was that it introduced me to a new style of 66 block. Usually 66 blocks have rows of 4 terminals with the two left ones having their opening facing to the center and the two right ones facing to the center like the picture shows below.
The block that the office I was working on was punched down onto though looked like this.
Notice how the three right most terminals face left and the 1 on the left faces right. On a normal 66 block, the two terminals on the left are bridged and the two on the right are bridged so you would punch the riser cable to the outside terminal and the jumper to the inside terminal allowing each side to be independent. On the block I found today it is actually setup to bridge all four terminals together. You put the riser on the left most block and can put up to three jumpers onto the three right terminals. From my research, it would seem this style of block was useful for shared lines.
I figured this might be of use to someone else that gets to deal with the inner workings of an old TDM phone system, even if it's just replacing it with something new.
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