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Best way to set up/cable a 551 KSU
#629269 04/20/19 12:15 AM
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Will H Offline OP
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So I have had a small key system up and running for a while, consisting of a 551c KSU and two 6 button phones. Each keyset plugs into a 66e3-25 block which is connected to a length of 25 pair inside wire running back to the KSU. I would like to add a dial intercom to the system via a Tone Commander intercom that I have. As many of you know, these 'outboard' intercoms will have their own 66 block to which the tip/ring and buzzer leads would be cross-connected to the stations. However, this got me thinking, the 551C is a small KSU, and it was intended that the inside wire/station cables would be run directly to it, as opposed to going through a cross-connect field of 66B and 66m blocks. So the questions I have are as follows; Was it common to have a cross-connect 'field' on small systems like this? What would be the best way to connect the leads from the intercom's block to the station cables? The backboard the system is mounted on is very limited for space. I was considering just getting a smaller intercom with a built-in 66 block, like a Melco MC and taking the necessary pairs from the station cables and punching them down directly on the intercom, to avoid having to set up additional blocks for cross connections. Hope this all makes sense.

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Re: Best way to set up/cable a 551 KSU
Will H #629276 04/21/19 02:49 AM
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What you say DOES make sense. That's the problem with the 551. As far as I know - and I was NOT a Bell Employee - The only Intercom designed for use with the 551 was a 401 (manual icm).

The 501 (which was manufactured by everyone) was big enough to have an intercom inside. Not so the 551.

Sam


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Re: Best way to set up/cable a 551 KSU
Will H #629283 04/22/19 12:24 AM
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I often used a 66B3-50 block mounted inside of a 25MH housing for these 551 KSU applications. I would punch down the 25 pair tail from the intercom unit down one side of the block. On the other side, I would create multiple appearances of T/R/L and LG appearances. Remember that since these were common talk path units, you could still use all four line card slots for actual lines and just extend the bk/gn, bk/sl and the appropriate buzzer pairs over to the block housing. For appearance sake, I would sleeve these pairs inside an empty piece of 25 pair cable jacket. Of course, there was also a 50 pair version of this block housing that permitted most station cables to terminate neatly within it and just one cable over to the KSU and Intercom unit were all that was left.


Ed Vaughn, MBSWWYPBX
Re: Best way to set up/cable a 551 KSU
EV607797 #629292 04/22/19 05:28 PM
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Will H Offline OP
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@Sam

Thank you. I was originally considering using a 401 ktu in conjunction with a 107 type loudspeaker or some small talkback speaker (knowing the 107 was only one way), but I decided the ability to place a initiate a call from both ends would be better.

@Ed
The use of a 25MH housing sounds like a good idea. There should be enough room left on the backboard to mount one. The use of an empty 25 pair jacket sounds pretty clever, too.

On a side note, was it common back in the Bell System days to have 1A2 services distributed to outbuildings? Basically, there is also a small outbuilding id like to have access to line 1 and the intercom. I don’t anticipate on putting a 6 button key set out here, but rather a 500 or 554 type wall phone. Effectively, lifting the handset would automatically go to line 1 and to use or answer the intercom, one would lift a plunger switch that would reset when the handset is hung back up. The problem is though, a 500 or 554 with a-lead control, two line capability, and a plunger switch, seems pretty rare. The building is fed by 6 pair PE89 cable that I Burris’s two years ago, terminated on a 116-type protector.

Any suggestions/creative solutions for the outbuilding phone would be appreciated.


Re: Best way to set up/cable a 551 KSU
Will H #629301 04/23/19 03:56 AM
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Sure, off-premise extensions were quite common with 1A2, either with special cards and single-line sets, or just a line appearance or two on a regular keyset. I think you'd have much better luck finding a regular six-button set, then using the first three pairs for the line (T/R/A/A1/LG and L), bridging the ringer on the T/R of the CO line and then using two pairs for the intercom T/R, L and buzzer. In this instance, you'd have to use the LG for line 1 as the LG for the intercom button AND BG for the buzzer. You could even shoot the moon (assuming that all six pairs are good) and put the ringer on the system's common audible output for the CO line instead.


Ed Vaughn, MBSWWYPBX
Re: Best way to set up/cable a 551 KSU
Will H #629306 04/23/19 02:35 PM
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@Ed

Thank you for the information. As crazy as it sounds, I'm trying to keep the system as 'historically accurate' to what Ma Bell would have done, as possible, so it's good to see that the outbuilding phone can still be done. All six pairs on the cable are good, as I buried it two years ago (I'm on a mobile phone, so it autocorrected buried to 'burris' for some reason). I will let you know how I make out with the system.


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