I have been researching the 551B KSU, and found on the net a copy of the BSP for this unit and printed it off. It made the wiring much more understandable. However, as questions are answered and I find the documentation, other questions come up.

The first is that the BSP states that there is an optional Frequency Generator (I am assuming it is a 'ring generator') that is listed as part 118A, and the mounting bracket part number D-18069. I am assuming (correct me if I am wrong) that the frequency generator will allow the individual stations to ring eachother. Would it be aventagous to find one of these generators?

The next question is this: can I only have four stations on this system, or can I daisy chain a couple extra phones per station? I know that the maximum number of CO lines is four, but I will stick with only two for this unit. It is not all that important to have more than four stations, because all I am trying to do is show off old phones in a working system.

Again, thank you for your patients with my many questions.

Best,

Joe

Joe -

I'll take a stab, although the experts will probably need to correct me.

I'm guessing it's a ring generator as well. As far as I know, it's not intended to ring station to station, but rather to allow all stations to ring (or I believe, if you want, buzz) on an incoming call. I'm guessing these were added to the KSU because as the number of keysets added to your system increases, the less likely the ringing voltage from the CO would be able to power your ringers. If you are only using 2 keysets you could probably get by without a ring generator (again, this is a guess), although I'm not sure how your ringers would be connected (the ringer leads come down the 25 pair cable on their own pair).

For the second question, as far as I know, there is no limit to the number of keysets you can connect (well, I should say I'm sure there is a limit, but in your setup, you'll probably never reach it).

I do know that you can feed multiple stations from one 25 pair cable (or, as you said, daisy chain), but if you intend to enable station to station intercom with signalling, the buzzer leads will need to be changed over to spare pairs inside the chained keysets, and then those will be the pairs you punch down at the 66 blocks for the intercom signaling functionality.

I think I remember reading that your KSU doesn't natively support intercom (could be wrong about that), but this problem is easily overcome with an external intercom unit. I have a Melco C-19, which provides the talk path voltage, lamp power and buzzer voltage to each station. I'm sure the folks here can point you to a source for a Melco intercom unit if you go down that path.

Hope this helped more than it confused -

Matt

Joe -

Matt is correct. The 551B is the "shoebox" style of KSU. It will hold 4, 18 pin 400 style cards and has a small power supply. The power supply has 24 VDC (unfiltered) to power the cards' relays, 10 VAC to power the phones lamps, 18 VAC that can be used to power buzzers for an Intercom and 24VDC (filtered) to supply "talk battery" for an Intercom. It does not supply 90-105 VAC for ringing.

The ringer in each phone can be connected directly to the CO line and that phone will ring whenever THAT CO line rings. But suppose you have two phones and three lines - How will you get all three phones ringing?

The answer is by using "common bell" where one ringer can ring on as many lines as appear on the set. This is done by looping the RG & RC leads from each card together and then wiring that loop to the ringer in the phone - but then you need a source of 90- 105VAC ring generator. That's where the external frequency generator comes in. It is actually possible to have a "common buzzer" system. Add a buzzer to the phone and wire 18VAC to the ringing feed for the cards. That's a little ...unusual, but certainly do-able. But yes, a ring generator is a good thing to have.

You can have a manual intercom in your system by using the 4th card slot in the KSU for a 401 type card. This will provide a talkpath between stations (but no signalling). Signalling could be handled by converting line keys to signal buttons or by adding external signal buttons to buzz other stations. With only a few stations this is very common. Your phones could be set up to have Line 1, Line 2, (a Spare key), Manual Intercom and a Signal Button (to buzz the other set).

You could also add an external dial intercom that would mount outside the KSU (like Matt has) that would be powered off the power supply in the KSU. These come in 10 station, 19 station and 37 station sizes (with expansion units available!)and come in Rotary only, Tone only or Combination Signalling.

You could have up to (I think) 17 or 18 phones in the system - more if you add lamp extenders - which is the limiting factor.

Hope this answers your questions.

Sam

Thanks for the info!

Does anyone know of a source for these frequency generators? There is one on e-pay that is getting rather expensive, but I am not sure that it is the correct device. I would rather buy this from either someone who is familiar with phone systems or a business that deals with phone systems.

Thanks again for the help!

Joe

I'll look in the dreaded basement. I'm sure someone here has one.


Sam

Well, all my "wall warts" (plug in transformers) are in a large bucket. Not quite a 55 gallon drum, but big enough. I'm pretty sure I have one, but if you really want one, post a request in the Buy and Sell Forum and if no one else comes up with one I'll dig one out.

Sam

If it is what I think it is, I've got one hooked up to my 1A2 system but I don't use the system too often...small black box about 2 by 4 inches with a set of screw terminals?

Hi Jeff,

Yeah, and it also has three places on top to screw it into the bracket. Had a very short cord with a plug that had an outlet on the back so that the KSU powersupply would plug into that. Neat design that looks like it could last several hundred years.

Joe

I mounted mine outside of the cabinet:

You can sort of see it on the bottom.

I have a new question: can touch tone and rotary phones (i.e. mix of models 2564 and 564) run on the same 1A2 KSU? If yes, what types of cards or what modifications must be made to the KSU? Thanks.

Just a guess, but I don't think it has anything to do with the KSU or cards; the only question is do your CO lines support rotary and DTMF? If so, mix and match away, you'll have no issues.

Matt1964: Great, thanks. How about in regard to intercom?

The line cards don't care. You need CO Lines that will support either. The 551B only supports a manual intercom internally (no dialing). If you add an external intercom then you can add a "C" style unit, it'll handle tone & rotary.

Sam

Sam: re external intercom "C" style unit, you mean something like a Melco KC-10X? See link:

https://www.reddialtone.com/images/melco_kc_10x.jpg

That's it. Besides Melco, Teltone and a couple of other folks made them, they worked fine. I still have one working in the house and use it every day.

You could also get a 207C (9 station rotary selector Intercom), a 216 (9 station expander) and a 247 unit. Wire them together and you'd get the same result as the Melco. (The first two were wire spring relay units and the third was PCBs). I don't think I've seen one of them in 30 years.

Sam

I am now the proud owner of a Melcom KC-10X intercom unit but I cannot locate a practice or manual for it (other than what's printed on the case itself). A push in the right direction would be appreciated. For example, the intercom has an AMP connector on the side which I presume should be connected to a block. My best guess is to use a 66B type block; does that sound right? As for the power requirements:
I recently purchased an old 551A KSU and will be hooking everything up over the next month or so for a home system:


Will the KSU supply the needed power for the external intercom unit? I'm new at this; please spoon feed slowly.

Thanks, all.

Mark

Mark -

So far you're on the money. There must have been practices for the units, but I don't have one, maybe someone else does, but they're really not that important. Plug in a cable, cut it down on a block, connect the appropriate power leads and then connect each station to Tip, RIng, Lamp, Lamp Ground and the appropriate signal leads.

A 66B block is perfect. That'll give you 5 connections for Tip, Ring & Lamp. If space is at a premium, you could also use a 66M block and then loop the T,R, L, & LG connections and multiple them on the other side of the block (that would actually give you 12 connections).

Yes, the KSU power supply has enough "oomph" to power the Intercom, and yes, A Battery is the Filtered and B Battery is unfiltered.

You could have the intercom signal with any voltage you like - 10V AC (blue wire buzzers), 18V AC (white wire buzzers), 110V AC (the ringers in the phone) or even 24VDC (Flat DC buzzers).

You're doing fine so far. Hang in there and ask away.

Sam

To add: The AB/AG and BB/BG connections are available on the lower right-hand corner of the block in the KSU specifically for this purpose. You can also use the LB/LG output for your +/- 10VAC audible (buzzer) supply. Just be careful to maintain proper polarity or you'll be blowing fuses.

I never thought I'd see the day that the 551a would be so popular again!

I thought this thread belonged in the computer forum for a minute! "basic questions"

And you can send GRD if the circuits require it.

Yup. Use the ground to close a relay to set off any device you want. My all time favorite was making the toilet flush (as I'm sure I discussed in an earlier thread).

Sam

Ed: You were right about the polarity and fuses. Oops. Now, I'm stalled looking for replacement 24E and 24B fuses which I'm having trouble locating in lots of less than 100. Do any of you guys have any ideas where I might locate replacement 24E or 24B fuses for my 551A KSU? Any help would be much appreciated.

Mark

Try the evil-bay.

Yeah, there's a store on E-Bay called "Jakes Old Western Electric Stuff". He has plenty of them and his prices are really good.

I confess to not remembering the nomenclature, and as I recall Buss did not use the same terminology.

Am I correct in thinking you are referring to the small flat brown fuses shown in the photos above?

If so, what Amperage and how many pieces of each are you looking for?

Sam

Thanks, Ed.

Sam: That's right; the little flat fuses. They're not easy to find. The 24B is 3 amps and the 24E is one-half amp. I may have found a vendor on eBay. He's checking his inventory now. The fuses look like this:



Mark


Mark

Well, I have a few down in the dreaded basement, I believe I only have 2, 5 & 8 Amp though.

If you can't find the exact sizes let us know and we should be able to tell you what you can safely substitute.

Sam

I would also recommend an eBay seller: Cougar Valley Phones and More. I have gotten a few phones from them and they a great resource- good stuff!

https://myworld.ebay.com/cougarvalleyhwt

If I still have any 584 panels you can have the fuses

Hello all.

I found the fuses and the KSU is back up and running. I've wired the CO lines to the KSU and have three stations wired to test. Everything works as it should except none of the stations will ring. I've researched the board and, since this 551A doesn't have a ring generator, I gather making station(s) ring has something to do with the yellow/slate pair. Some questions:

1) Assuming the above is correct, where do I punch down the yellow/slate pair? To T/R where the stations connect or to the T/R where the CO line is coming into the KSU (or elsewhere)?

2) From what I've read, since there's no ring generator and the CO lines provide ring voltage, I may have only one station ring (per CO line) in that configuration. Why is that? After all, five or more SLT's will ring with only the CO ring voltage to work with. What concept am I missing?

3) If I cannot have more than one station ring per CO line, can I use the 10v buzzers (as used for the intercom) as an alternative? If that is a solution, what wiring is involved in making the phones buzz to signal an incoming call? Can a ringer be used on one station and buzzers on others?

If any of my assumptions don't seem quite right, I welcome your corrections and advise. Thanks for all the help so far.

Kind regards,

Mark

Mark,
1, I'll pass since I don't have a copy of the practice. Generally, the bells (or buzzers) are wired to the Y/S pair in the phone and connect to the "Common Audible" source, in the KSU or on a 66 block with provision for cross connecting to multiple Y/S pairs from phones.

2. The problem is that you cannot have more than 1 C.O. line connected directly to the same bell. If you only have 1 C.O. line in the system, then sure, all the phones can ring on it. But, if you have 2 (or more) lines and you connect them to the same bell (or bells), they will act as if they are conferenced together and tie up so that you will not be able to call out and callers will get a busy signal.

3. Yes you can use 10 or 18 volt buzzers for C.O. ringing. It just takes the correct wiring in the KSU, (again,see the practice) and buzzers rather than bells on the Y/S pair in each phone. In fact, most business 1A2 systems I installed were deployed that way.

Mark -

The Y/S pair is wired to the ringer in the set. You have a number of choices available to you.

1- You can wire the Y/S pair to T&R. It can be either T&R in or out, either will work.

2- You can buy a Ring Generator and add Ringing to the system and then wire the Y/S pair to the Common Bell output from the Line Cards and have each bell ring on more then one line.

3- You can use another voltage besides 90V Ringing Generator as a ringing source. For example you could use 10V or 18V AC or -24vDC, all of which are present in the power supply that you have. You would then have to use a different ringer then the one in the set. It could be low voltage buzzers (either AC or DC) or a low voltage bell or whatever else you like.

As John said, you could have more then one bell ring per line, but you can't have more then one line ring per bell - unless you use the Common Ringing circuit from the line cards and yes you can mix bells and buzzers and gongs and chimes and lamps and....whatever else you want.


Sam

Well, you actually can ring multiple lines to a single set of ringers if you are using 400D cards. You'll need to strap the options on each card for steady ringing. Then, you will need to strap the ring side of each line in as a back-feed to each CA lead for each line. Using the RG/RB output from the KSU (the last pair on the bottom-right side of the KSU's block) that is connected to the ringer(s), you'll be able to accomplish this.

This also assumes that you have a good ground to the KSU and you are using real CO lines, not fake VOIP or CATV ones.

Ed -

That's a pretty wild trick!

Sam

I have a standard Tellabs 8101 ringing generator (used) if you would like to go that route. They mounted better in a 584C panel though. You can PM me if you are interested.

I DO have a 118a RG laying around...if you still
need one.

Key system that will last forever. No software bugs there. Just someone wiring it wrong!'

ohhh my...you mean these things still have some value?? I just disposed of three or four of these...bummer...

DT98