sundance-communications.com/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems KTU issues

Like Bruce Wayne...?

Yes, exactly like Bruce Wayne!!

Earlier Arthur stated, "This suggested cabling method ranks among what is one of the stupidest suggestions ever found in a Bell System practice. Don't even think of doing it that way. Use one 25-pair stub cable, cut down in the KSU, and terminate it on a 66B25 block, outside the KSU. Then terminate your station cables, two per block, on 66M50 blocks. Run cross-connections from the feed block to the station blocks. That will allow you to energize ten stations."
Arthur, if you can indulge me one more time,(I have 2 empty columns on my KSU) can you tell me why I can't just hook my KSU to two 66M50 blocks and then punch down 3 cables to each one? I guess I don't understand the need for the 66B25 and what role it actually plays. It would seem that my method would at least give me 6 additional stations which is probably all I need whereas what you described would give me 10.

Bill -

Yes, you're correct. You could feed 6 stations off 3 M1-50 blocks (using bridging clips). Arthur's suggestion of the 66B4-25 block is the method we all liked best, because it gave you the most flexibility. It was always my experience that when you allowed for 6 stations, you somehow always needed 7, or maybe 8.

We often put 2, 66B4-25 blocks in, side-by-side, with the feed pins touching. Then we would loop one side and punch down the other. Allowing us 10 pins (20 stations!) with only one feed cable. No one ever went broke assuming extra stations would someday be installed.

Sam

Sam, if I may ask you one more question: I know what the A, B, C, and M designations stand for, but what is the difference between a -25 and -50 block? Thay both have 66 pins per column. The only difference I can see is the -25 is electrically connected between columns 1 and 2, and 3 and 4 but the first two columns are electrically isolated from the last two. In the -50, all the columns are electrically connected.

Yup, the -50 block is commonly referred to as a "Split-Block". You can terminate cables (a single 25-pair, or 6 4-pair, or 8 3-pair) on the outer column of either side. Then you can run jumpers to the connected columns and have each outside cable independent, or you can run your jumper to just one column and use a bridge clip to connect to both cables on the outside columns.

66 blocks do not have 66 rows. They have 50 rows, generally. Sometimes fewer, like 32 for a 16-pair cable, or 12, for a 6-pair cable.

66B25 and 66B50 are the last iterations of the blocks that are bigger. (More space between rows than the "M" [mini] blocks do, so they are physically taller, and take more room on an MDF.)

M blocks come in 25-pair versions, (4 pins across each row, all connected) and 50-pair versions (two sets of 2 pins in each row, left side insulated from the right side.)

My suggestion to remote the outputs from the shoebox to an out-board block has little to do with electricity, and more to do with physical convenience and trouble avoidance. It was said to rebut the notion of trying to cram 10 cables (wired using the loop-through method) into a shoebox.

After having wired approx 10K key sets in my lifetime, my method is to provide a source block (generally a 66B25, for ease of counting and 5 useful outputs) and to provide a 66M-50 split block for every 2 key sets. Then, cross-connections are run to take the features from the source block, and assign them to the key sets.

If you do that once, you have accommodated 10 sets. You can do it 4 more times, from a shoebox internal block, and energize up to a total of 50 key sets. More than a sane collector would want hooked up at one time. I, of course, am not quite sane, and have 20 or so key sets hooked up right at the moment.

I hear you. I still would like a method to isolate my KSU except for the CO lines so if I wanted to change it to another KSU, I could simply unplug the Amphenol connectors and do it. But that is down the road, just trying to get all the wires run and all the stations hooked up. Thanks to all for your help.

There is no reason why you couldn't have a 25 pair feed tail with a female amp connector coming from the KSU to the first 25 pair block, such as 66A25 or 66B25 and have, as the first connection to the block a 25 pair cable terminated to a male amp connector. This will facilitate being able to quickly change out the KSU for another. You can also use M blocks with a built in 25 pair amp connector on it, but that kind of makes an additional point of connection that is unnecessary. The method Arthur described is an excellent method of building a good, serviceable key system cross connect field.

Rcaman