atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems KTU issues

Bill:

I believe you can use more than four basic types cards in a 551 KSU. However, some cards may require a change in the wiring/connections in the KSU so that the right voltage goes to the right pins on specialty 1A2 line cards. Generally, if you were a customer who needed such special features, Ma Bell would have installed something other than a basic 551 shoebox KSU at your premises.

Thanks,Arthur, but without sounding too stupid, what is an MDF?

https://en.wikipedia.org/wiki/Main_distribution_frame

The backboard that is centrally located, equipped with terminals where all your key system, station, and central office cables and connections appear. It's where you make the cross-connections that bring dial tone to the equipment, and features to the stations.

https://sundance-communications.com/forum/ubbthreads.php/topics/568832/Photo%27s_of_large_1A2_system_an#Post568832

Here is a posting from this very 1A2 sub-forum from earlier today. It is from my friend Phil who has a huge PBX and key system collection. Click the link that he provided and you will see a large key system MDF.

And thanks, Phil, for your insight. While we are talking about this, I know the 551 has only 4 slots for cards while the 256x has 5 keys. Is the fifth key for a separately wired intercom such as the Melco or Tone Commander? Or what else could the fifth key be used for and how would it be wired?

Arthur Bloom stated earlier: "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."
I found some of my connecting blocks: Have 4 Siemon Co. S66 M and this is the one I said had 4 Amphenol male plugs wired to each of the 4 columns. Is this useable in what you described above? Also have a WE 700A-66-B1-25 jack where the 4th column is wired to a female Amphenol connector. Is this anything like you described above? Sorry to say, all these 66 connecting blocks look alike to me and I don't understand the nuances between them.

Those blocks are made for specific uses. There are all sorts of subscriber and central office applications that use 25-pair connectorized cables. They are not generally used in 1A2 installations. The blocks to use to terminate key equipment are 66B25, and the blocks for station cables are 66M50.

It's just the way it is that there are 5 line keys on a 565 set and 4 slots in a 551 KSU. I think you're trying to read too much into all this. These systems are made for growth, and the number of keys versus the number of slots is not correlative. There are 3-line sets (54x series) 5-line sets (56x series) and 9-line sets (83x series.) There are Call Directors that come with 5, 11, 17, and 29-line capacities. There are 584C panels that provide 13 slots per panel, and they can be multipled infinitely.

If a subscriber needed a couple of lines and a manual intercom, a shoebox was prescribed. The original 1A1 systems (301-type KSU's) had line circuits for 4 CO lines, and had a dial selective intercom (207C) unit factory-installed. So in that case, the phones "matched" the KSU, but it was just a coincidence.

When 1A2 was introduced, and a shoebox was too small, then the installer would put in a 501, which has room for a 207C, and a 216A. Some 501 types came with a prewired power unit, and some didn't.

In later years, packaged intercoms and other packaged devices like amplifiers, service observation units, and special relay assemblies were designed to fit between the 7" space between the horizontal bars of a 501 and other cabinets like the 16C.

I plan on using 2 415s KTUs in the same KSU (620a modular panel). - What is the difference between a 415A and 415B?
- Can I use one of each in the same KSU?
- Lastly, I can't find the BSP that gives the specifics on it; I found many references to it in other BSPs. Any idea of the actual one for it?

Thanks all!

B. 415-Type KTU (Automatic, DC Signaling, Private
Line Circuit) (
2.23 The 415A (MD) and B KTUs are 4-inch,
18-contact KTU s for connecting stations in
the system to a private line terminated at a distant
station. Another 415-type KTU, or other private
line KTU which will respond to a de signal, is
required at the distant end. The 415-type can be
installed in any of the CO/PBX jacks of the 680B
Qnly. Do not use a 416-~ype in the 680B
KSU if music-on-hold is· furnished. The
580A does not have "A" battery and ground wired
to these jacks and, therefore, will not accept the
circuit. Additional information on the 415-type
KTU can be found in Section 518-215-400 and
CD/SD-69559-01.

Google ITT 415 KTU. It has a complete KSP (ITT's version of the BSP). See the above paragraph (BSP 518-215-400 for info on the WECO version.

It would appear that the 415B is just a later version, perhaps created to eliminate the problem I mentioned earlier with signaling over carrier. I don't know if the "A" and "B" versions are compatible. Probably, but......

Sam

Thank you all for your your insight on this!

One other important point about 415 cards and tie lines:

Before Caller ID when your phone rang you had no idea who was calling. Unless you had a tie line/hot line. Then you knew exactly who was calling.

On Wall Street traders "turrets" (giant key phones) almost all the circuits were hot lines. This way when the phone rang the trader could decide if he wanted to put his current call on hold or ignore the incoming call.

Same goes for corporations. Was the factory/headquarters/whoever calling or was it.......someone?

Notice the name: HOT line. Someone important. Someone who was willing to pay the freight for mileage charges so you knew who was calling.


Sam