Can anyone point me toward schematics for the old 1A2 key systems?

We had equivalent multi-line systems here in England and I'm sure the switching elements are very similar, but it would be interesting to compare in detail as I've never had a chance to study 1A2.

The only drawings I'm aware of are the ones in the 1A2 manuals, which you can find on the Internet, but they are pretty pricey. I don't remember a schematic drawing only for them like there was for 1A1, but could be wrong.

Bill,

Apologies for the late response; I hadn't set reply notification.

I don't think it's worth me trying to track down full manuals and order in that case. Perhaps somebody could give me a quick overview of the basic 1A2 wiring for reference.

Obviously each line requires tip/ring pair, and I think I've gleaned from other posts that a second pair labeled A/A1 is used as the holding circuit through an extra set of hookswitch contacts. Presumably a 3rd pair for the line lamp, although something about lamp returns being commoned in some cases?

From a phone standpoint, each line needs Tip, Ring, A and Lamp. In fact, in 10-button sets, the grounds come in on the first line(a1,LG) and then the rest of the lines get only T,R,A and L.
When we wired for 10 button sets, we only had to use two-pair, instead of 3-pair after the first line. Geeze, no wonder I still have that 3-pair cross connect wire in the warehouse :-)

There's a pretty good reference to 1A2 with diagrams at https://www.kadiak.org/tel/1a2.html

Carl

Check this out it was provided by usroute12 in the topic of 620A2 ksu's, he found a site to get the individual practices, still pricey but not near as much as the full manual.

Excellent, thank you! I printed out some of those diagrams and studied them last night.

I take it that the line cards went through different versions over time (e.g. the 400E appears to dispense with the A relay of the 400D) and that third-party vendors offered their own versions which were directly compatible.

A few of the options pose some questions. The 400D KTU diagram shows a 30-second ring timeout option by omitting any resistor from the 1/2/3 terminals. Was this just a consequence of giving maximum flexibility by having a very high value resistance on the card, or a deliberate design feature to allow such a long delay? 30 seconds seems awfully long given a standard 2 on/4 off ring cycle. The only place I can think of where one might want such a long timeout would be if the C.O. line was on a manual board with non-machine ringing which might be of variable timing.

I see the BR link options to have the L relay operate from normal ringing on the C.O. line, but when/where were the remote A.C. and remote D.C. ringing options used?

Paul -

It's been a real long time, but if I remeber correctly the remote options were used if you wanted to close a relay to operate some other type of ringing device. I'll try to dig up some prints at home over the weekend and check.

Paul:

AT&T/Western Electric's line cards were 400A, B, D, G and H. The G version had a blue handle and an "in-use" LED. Also, options were changed using yellow plastic jumpers instead of wire jumpers. The H version was a 100% solid state version of the G, as in having no relays or other moving parts.

The ring time out options were to accommodate the various central office switch types or PBX's that may be providing the line. The long time out option was eliminated with the introduction of the G version in the late 1970's since most older offices, PBX's and cord boards were being phased out by that time.

Generally speaking, the 400E was exclusively ITT's nomencature, and F was San/Bar's. All card brands were interchangeable between systems with a few minor exceptions.

Card slots could be equipped with a manual intercom (401A or B) card. This basically provided a simple coupled transformer arrangement to create a talk path. These were used for button/buzzer type intercom systems. The problem is that they required filtered -24VDC "talk or 'A' battery on pins 3 and 18. Since ITT's and San/Bar's cards had music on hold capability through these same pins, care had to be taken to ensure that talk battery wasn't present on these pins in the slot. Failure to do so surely resulted in the MOH circuit being blown very quickly. Most AT&T/Western Electric systems had these pins factory-wired to the "A" battery output of the power supply, but ITT and San/Bar kept them isolated for field connection if needed.

1A2 permitted the ringer in the telephone set(s) to operate directly from the CO line ring voltage, or in larger systems, ringing could be generated internally and follow a slightly faster cadence. This was accommodated through the use of the relay contact, the motorized interrupter and a local ringing generator (they referred to them as frequency generators). I was told that the reason for this faster cadence was to give employees the perception that the phone line was ringing longer than it really was. I have never verified this to be fact.

I can't figure out the logic behind the J1 jumper option on the San/Bar schematic (Model 4200A with music-on-hold) at all. Pulling the BR (Bridged Ringing) jumper appears to leave the C.O. tip (pin 14) completely isolated from everything except the holding resistance and MOH circuit; the ringing section of the L relay via its associated rectifier (and blocking capacitor if A.C. ringing option selected) is then just connected across station side tip and ring. :confused:

I've browsed through some of the older threads in this section and seen some references to that. Was this just one of the lines to each phone assigned to the internal intercom so that anyone could pick up the intercom by just hitting the appropriate line button?

I also saw mention of a dial intercom card. I'm assuming that this was a similar card which provided not only talk battery for the intercom line but would also recognize DTMF tones (or even pulse?) to sound the appropriate buzzer for the required station.

I note the quite versatile signaling arrangements possible, either a low-voltage audible or conventional A.C. ringing with diode matrix to provide intercom isolation and/or split the ringing for phones not provisioned with all C.O. lines.

Presumably the M jumper to pin 18 on the 400E line card is for MOH. The DR option on the same card appears to apply -24V to pin 3 only when the line is in use/held or ringing (i.e. L relay operated). I'm still trying to work out possibilities for the RU and TU options!

The British Post Office supposedly adopted the double-burst ring {*} which is standard here because it resulted in subscribers answering more quickly. Many PBX systems, and some of the small public exchanges had single-burst ring though, generally where the timing came from an interacting relay set rather than a ringing machine.

{*} Standard cadence is 0.4 on, 0.2 off, 0.4 on, 2 secs. off.

Man, Paul! You definitely have this stuff under control. I'll do my best to answer with what I know:

As for your first question about the 4200A card, I really don't know for sure, but I'll take a guess. I don't have any of their schematics left to review. Bridged ringing and grounded ringing were options when party lines were still around. They were definitely present when 1A2 was popular. I am assuming that this option was to select between the tip side of the line or ground for ringing voltage reference. Again, that's a guess.

As for question #2 about the manual intercom: Yes, this was just a common open talk path that appeared on a line key through traditional 3-pair cross-connects. These were generally set up as private talk paths between an executive and a secretary, but anybody with an appearance of this "line" could barge in. Very frequently, the locking screw of an unused line key could be removed to become the pushbutton to buzz the other station. A momentary ground (A1) was simply placed upon the line key's A lead while pressed which closed the circuit to the buzzer at the other station.

In cases where multiple stations were involved, "side cars" of buttons were added to the phones and spare leads in the line cord were used.

Yes, there was a dial intercom card made by ITT and San/Bar that fit the standard 1A2 "sized" card slot. This card, while similar in size, could not be installed in regular slots; it had to be a dedicated slot. Western Electric had a 424C and later 494A card for dial intercom, but it was an 8" card as opposed to the traditional 4".

Yes, the ITT and San/Bar cards had option jumpers to select MOH. Their factory setting was no MOH, so one would have to change them and hopefully during this process, think about checking for the presence of A battery.

I like the older equipment!

That did cross my mind. I can apply it to the 400E card: Pull the BR jumper, install TU and RG (Ringer Ground?) jumpers and the ringer relay is then tip to ground. Presumably you'd then just swap incoming tip/ring connecitons for ring-to-ground ringing.

I can't figure out anything like this on the San/Bar card though. I'm looking at the diagram from Carl's link:

https://www.kadiak.org/tel/4200a.jpg

As soon as you pull the BR link, the incoming tip side of the line doesn't seem to be going anywhere except the hold circuit via relay contacts K1A.

I think (it's been a long time)that the BR leads only strap the ringing to the CA (Common Audible).

Man, in late 1983 & early 1984 we were getting the brand new San~Bar "400" or was it "4000" cards delivered to us in the Air Force with Music On Hold (MOH) enabled by default. This was a major problem considering we did not use MOH at the base I was stationed at in those days. For some reason the cards put a hum on the line that was unbearable until we disabled the MOH feature.

The BR straps on the 400E diagram make sense, but according to the San/Bar diagram the BR strap just connects C.O. tip to station tip. As far as I can tell, if you pull the BR strap there's just no way you'd ever be able to use that line. :confused:

A couple of other points. First, I notice that all the cards have hold-release options of 50mS and 500mS, with the former being indicated as for use with ESS offices. Did all offices guarantee a minimum battery-drop period of 500mS upon calling-party hangup, or was ESS actually shorter? Obviously SxS/panel/X-bar might give momentary battery loss during relay switching which would necessitate the longer timeout, but as ESS (presumably) only dropped battery deliberately, was the 50mS a necessary setting on the line card, or simply a permissible setting but ESS still gave the full 500mS drop?

Second, and perhaps more simply, how often did customers specify the steady hold light rather than wink?

I do know that the "long" setting was intended for ESS offices. I don't remember ever having to change this setting whether the line was from an ESS or crossbar office.

The BR strap and B/R leads are two different things, but it appears that they both have been sufficiently described here.

Paul -

Before 1A2 there was 1A1 (Wire Spring Relay) and before 1A1 there was 1A (Flat Spring Relay). Under 1A (and I think 1A1 too) if you wanted wink hold it required another relay.

Additional relay = additional monthly charge.

Telco's charged extra for Wink hold and also (if I remember correctly) for Incoming Flash.

So, if you were upgrading a customer from relay to PCB and they weren't paying for wink/flash you needed a way to downgrade them.

Sam

Sam:

I know exactly what you are talking about. In New Jersey, I used to encounter those 1A1 setups all the time. That "system" was completely line-powered, so there really wasn't a way to power the lamps anyway. What made it even more fun was that it was field-constructed and those little metal housings for them were frequently placed in ceilings and nearly impossible to find!

They definitely charged an extra monthly fee for flashing lamps. I remember that well when I was renting equipment from NJ Bell at my home.

Ah, I see. The phone companies really liked to charge for every possible extra. I guess if customers moving to 1A2 were given wink-hold for free then existing 1A1 customers would have questioned why they were still paying extra.

I think locating 1A1 diagrams to study will have to be my next project.

Paul -

Someplace at home I have a Bell Systems book with drawings of 1A1 & 1A2. I'll see if I can dig any out and pdf them.

Sam

Many thanks Sam, that would be great!

Paul -

I have scanned about 15 pages of 1A (Flat spring relay) documents into a PDF file. I'm not sure how good it is going to be - I'm scanning from a bound book, not loose sheets of paper. The book is called "Key System Service Manual, Vol. II" It's about 500 or so pages of small print and schematics.

I'll try to do some 1A1 if this works. PM me with an email address and I'll send it over to you.

Sam

Many thanks Sam, very much appreciated.

PM sent.

Just some additional notes on line cards and general 1A2 goodness. Ed, you may find this of particular interest.

The Western Electric 400H (last of the 1A2 CO/PBX line cards) actually did have one relay. It was a tiny mercury-wetted beastie, though I don't recall what it was used to switch (gotta check my SD's to determine that).

I have had problems with 400H's, enough so that the 400G is pretty much the only one I use now. Most of said problems were related to incoming ring detection, and detecting the momentary CPC drop from the CO when a party on hold hung up.

It is my opinion that the 400G represented the last of the 'good' cards out of WECo.

I've had great results with the SAN/BAR 4200's. I still have a couple as spares. Also, I have the unique distinction of still owning a SAN/BAR 4201 FM receiver card. I actually bought the thing, at list price, brand-spanking new from a local supplier back in the late 70's.

Although I am using music-on-hold at the moment, I'm not using the SB cards to accomplish it. I have a wall-mounted receiver from Valcom, coupled to a pair of WECo 109B 'Audio-on-Hold' cards. I would add that the 109B's seem to be particularly rare in the 1A2 KTU world. I've not found any BSP on them, and ended up ordering the SD's from the Lucent CIC just to figure out how to hook them up!

On that note... I have a couple of other posts to make on other topics. Keep the peace(es).

Geez, it figures that you would have caught that! Yes, even the 400H had a reed relay to detect incoming ring current on the line. Man, I can't pass much of anything past you, Bruce!

I agree that the 400G was by far the most stable and reliable line card. There were too many revisions of the 400D and for some reason, our site situations always required a different revision. Sort of like Partner systems. Whatever you needed, you didn't have the correct revision.

I think that the only reason that the 400G went away was because dedicated phone equipment closets started to go away in the early 1980's. At that time, equipment had to start being installed with in the office space. The clicking of relays might have been objectionable, resulting in complaints. The 400H was virtually silent in operation.

Hey, I am just guessing.

Ed, hate to burst your bubble but, clicka, clicka, clicka. The sound of a mechanical interrupter. ITT601 had an electronic one. Did the shoebox W/E have a mechanical or electronic interrupter? And is my mind going to lala land or did Sanbar really come up with an electronic plug in for the mechanicals? John C. (Not Garand)

Man, everyone is out to beat me up! OK, I was referring to the card itself being quiet without having any mechanical relays. Yes, John, all WECO 1A2 and Comkey systems used mechanical interrupters. Their 6B "Dialog" advanced intercom system was sort of a PBX/intercom system hybrid that offered solid state ringing and lamp flash, but it was short-lived. Tone Commander's ML-8000 beat it up price-wise, so I doubt that the 6B lasted more than five years.

I know for sure that ITT's 601 had a solid-state interrupter and that was the only option. I bought enough of them to know. These cards had a very high failure rate due to heat issues.

The San/Bar one fit into a dedicated slot on their own 15-line panel and wasn't interchangeable with other systems, but it was definitely solid state. I am pretty sure that Plant Equipment made a solid state interrupter as well for their panels, but I never worked with them.

I guess they wouldn't have been happy with a Strowger PBX rack occupying one corner of the office then?

Uh, no....I seriously doubt it Paul!

I have the big page manual on the Horizon. It's in a three ring notebook. At that time, it was the The technicians go to. The Station practices version was
not as easy to understand.

If anyone needs old spring relay specs or anything dating back to a 701. I have the various manuals.

I most likely can dig up some old cord board stuff that can give a schismatic of reference.

Just a thought

Ed, your comment about the 601 electronic interrupter dying, brought back memories. We had 5-6 in stock, just so we could do the old swap and send for repair. Those things were about as reliable as Fiero headlight mechanisms! And who got stuck changing resistors in ITT701 station cards? We actually had 2 systems we never installed because we used the station cards for swapouts. We were 1 of the few interconnects that were allowed to change out the resistors, after the 1st couple of months. Apperently, a lot of PCB's were destroyed with soldering guns! We clipped out the resistors and then removed the leftover leads, instead of trying to salvage the resistors. Like, what are you going to do with the old ones, start a used resistor sales depot? And of course, we had bench component level repair for Code-A-Phones, so we knew how to R and R components. John C. (Not Garand)

Same here, John. Every truck had at least one of the 601 interrupters on-board. I might add that those bad-boys weren't cheap. We never worked with the 701, but plenty of 801's.

As for the Fiero headlight mechanisms: My wife drives a 2000 Trans Am in pristine condition. Her headlight mechanisms began to fail about 4 years ago and I ended up finding a guy selling repair kits on e-bay. They are the same units as those used in the Fiero. Never had another problem since, in fact they actually work better than they did originally.

Ed, just came back to see your last post. At the risk of being labeled 'Highjacker', I contend that the Fiero is HIGHLY collectible. First, and until recently, only rear engine sports car U. S. mass produced. (And don't try to slip the Corvair in here, that dog won't hunt.) All fiberglass and affordable, at least initially, for the unwashed masses. It's technology is nothing to write home about, but....? And I work with a guy that had one with a small block V8 in it and it would lift the front wheels off the pavement for a few inches! He said a mechanic friend put it in, he got a load of tickets and had the friend put the original engine back in. Eventually sold it, it was just to much trouble in the family, even with the original engine. John C. (Not Garand)