Author Topic: Connecting a 51AL to a 684A  (Read 6925 times)

Offline poplar1

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Connecting a 51AL to a 684A
« on: February 14, 2013, 06:28:55 PM »
Sometimes you need to connect an older candlestick phone to a more modern subset than was originally intended.

For example, you have a 20AL (non-dial) or 50AL (dial) or 51AL (dial), or 102, but the subset you have (634A, 684A, 495BP, or base of a 302 phone used as a subset) was intended for a 151AL, 202, or 211.

In short, you are trying to connect a sidetone set to an anti-sidetone subset. The sidetone set has only 3 wires, but the anti-sidetone subset is looking for 4.

There are two ways to do this:

1. Move the black condenser wire to Y/L2. (Normally, there would be  a connection between the black condenser wire and Y/L2 only when the phone is off-hook and the dial at rest.) This provides an anti-sidetone circuit.

This arrangement is restricted to only one phone (no extensions) and two high impedance ringers (B1A, 78J) or one low impedance ringer (8A, 78A).

--OR--

2. Without changing any wiring in either the phone or the subset, connect the cord from the phone as follows:

Yellow to GN on the induction coil.
Red to L2/Y on the induction coil.
Green to BK (along with the black condenser lead). (Use spare terminal GND for both wires if using a 302 base.)

EDIT: ALSO MOVE RED CAPACITOR WIRE FROM C TO L1.


This provides a sidetone circuit.

Reference:
Bell System Practices
Station Installation and Maintenance
WR-C63.373
Issue 1, 9-30-42
AT&T Co

WR= Wartime Requirements
« Last Edit: November 30, 2013, 11:51:57 AM by poplar1 »
"C'est pas une restauration, c'est une rénovation."--François Martin.

Offline poplar1

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Re: Connecting a 51AL to a 684A
« Reply #1 on: October 07, 2013, 07:00:53 PM »
The following information was left off the previous post:

The red incoming line should be connected to C---and not L1.
The red ringer wire should connect to C--and not L1.
The red talk capacitor lead should connect to L1--and not C.

Again, this is for a sidetone phone (20AL, 50AL, 51AL, 102) using an anti-sidetone subset (684A, 634A, 302 base, etc.).

If anyone has a chance to verify that this works, I would appreciate it.
"C'est pas une restauration, c'est une rénovation."--François Martin.

unbeldi

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Re: Connecting a 51AL to a 684A
« Reply #2 on: October 08, 2013, 01:00:50 AM »
The following information was left off the previous post:

The red incoming line should be connected to C---and not L1.
The red ringer wire should connect to C--and not L1.
The red talk capacitor lead should connect to L1--and not C.

Again, this is for a sidetone phone (20AL, 50AL, 51AL, 102) using an anti-sidetone subset (684A, 634A, 302 base, etc.).

If anyone has a chance to verify that this works, I would appreciate it.

A circuit diagram would make this a lot easier to follow.
There is a complete circuit for this in the addendum B (1946) to BSP C63.373, which  seems to be your first wiring option in the previous post. This is an AST circuit. There is just one problem with this, the circuit would always be connected to the line, as the hookswitch is insufficient to cut it off, and therefore it AC-loads the local loop even when on-hook. The  Addendum warns of this only by a restriction, not an explanation.  If the hookswitch has an additional contact pair, this could be used for remedy, otherwise one could bypass the hookswitch in the talk circuit and use it to cut off the line.

In your second choice, I think you are replacing the normal primary coil L1-R with coil C-GN, which is probably ok for today's circuits since the resistances of the two coils are very similar, 22 Ω vs. 19 Ω when using the 101A coil. However, the turn ratio is 70% only (secondary coil vs. primary) and so you probably get a different gain of the circuit.

If I got your wiring wrong then I really need to draw a circuit.
« Last Edit: October 08, 2013, 01:33:53 AM by unbeldi »

Offline poplar1

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Re: Connecting a 51AL to a 684A
« Reply #3 on: October 08, 2013, 03:54:57 AM »
The truth is, almost all metal---634-type, 434A-- and Bakelite WE subsets--684-type--on Ebay are anti-sidetone (AST).  [302 bases used as subsets are also AST.]

Most desk stands (candlesticks)--20AL, 40AL, 50AL, 51AL--are sidetone (ST). Thus there is a compatibility problem: the ST phone has a 3-conductor cord but the AST subset requires 4.

If you have a 102, you can just change the cord from 3-conductor to 4-conductor to make it a 202. But you can't do that with a 20AL or 51AL because there aren't enough switch hook contacts.

So in 2013, as in 1942, we find there are not enough sidetone subsets (534A, 295A, 334A, 584A) available for the supply of sidetone desk stands.

The first option above--"to obtain the equivalent of an anti-sidetone circuit"--is restricted to "individual lines without extensions." (Basically, the black capacitor wire is permanently connected to L2 rather than only when the phone is off-hook.)

What is significant in the WR practice is the additional wiring option: "to obtain the equivalent of a sidetone circuit"--without restricting the use of additional phones on the same line. While this additional sidetone might seem less than ideal, still, in 1942 as now, it permits us to use what's available on hand.
"C'est pas une restauration, c'est une rénovation."--François Martin.

unbeldi

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Re: Connecting a 51AL to a 684A
« Reply #4 on: October 08, 2013, 03:51:30 PM »
Ok, here are circuit diagrams of both wiring options you presented. These are diagrams for connecting a side-tone (ST) desk stand with a three-conductor mounting cord to an anti-sidetone (AST) subset with a 101A induction coil. The ringers are not shown, as connections are trivial and always bridge tip and ring. The diagram shows the windings of the induction coil in-phase at the *-marked terminals (P*,*S,*T).

I kept the position of all components fixed between the two diagrams, it makes it easier perhaps to compare, but this does not provide the best layout for the second diagram.

The state of the desk stand in the diagrams is on-hook; when off-hook, the hookswitches HS1 and HS2 are closed to complete the circuit.

1) The first diagram is drawn according to BSP C63.373 Issue B 3-20-46 N.Y.Tel.Co.  This circuit provides some sidetone suppression on the ST set, but has the disadvantage that it permanently AC-loads the local loop with a very low impedance, so that no other stations or extensions may be connected to the same line.

2) The second diagram is your wiring modification to use the 101A induction coil for ST service. It has the advantage of not loading the line, as the telephone is completely removed from the line by the hookswitches, with the exception of the ringer of course (not shown). The circuit innovates as it uses the normally tertiary winding (C-GN) as primary in the transmitter (TX) circuit between tip and ring. Since the T winding has a slightly lower DC resistance, we expect the transmitter current to be almost 15% higher. The receiver (RX) circuit now has all three windings in series in addition to the condenser, so the impedance is pretty high.

Have you tried this circuit for reception?
« Last Edit: September 02, 2017, 05:00:58 PM by unbeldi »

Offline poplar1

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Re: Connecting a 51AL to a 684A
« Reply #5 on: October 08, 2013, 08:24:00 PM »
Hopefully others will report back on the results they've had with this circuit.

This is not my circuit, but rather the one shown as "51AL Sidetone Desk Stand For Sidetone Service" in WR-C63.373. (The only thing I did was to be a pinch bidder for w***e--he must have been asleep that day in Aug. 2012 when I won this manual.)

I tried this circuit with an 51-AL and an just an F-1 handset by itself. Also with an 151-AL without the black lead connected. (Not connecting the black lead from AST 151AL or 202 to subset makes it equivalent to a sidetone 51-AL or 102).

The only problem was with one set which has a 337 transmitter: the sidetone is very loud. However, this appears to be characteristic of the transmitter itself and not the sidetone circuit.



« Last Edit: October 09, 2013, 01:02:35 AM by poplar1 »
"C'est pas une restauration, c'est une rénovation."--François Martin.

unbeldi

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Re: Connecting a 51AL to a 684A
« Reply #6 on: October 09, 2013, 02:53:44 AM »
This is not my circuit, but rather the one shown as "51AL Sidetone Desk Stand For Sidetone Service" in WR-C63.373. (The only thing I did was to be a pinch bidder for w***e--he must have been asleep that day in Aug. 2012 when I won this manual.)
Oh, I see, I didn't realize both were taken from the BSP.  So, what was/is the significance of these WR-BSPs? Would you share a scan? Is there any explanation of the 2nd circuit?

What is the resistance of the 337?  It was intended for long subscriber loops vs. the 323, so perhaps it has a lower resistance to boost the talk current, and since this circuit also has a lower resistance in the coil, perhaps this raises the sidetone too much.



Offline poplar1

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Re: Connecting a 51AL to a 684A
« Reply #7 on: October 09, 2013, 06:57:30 AM »
WR= Wartime Requirements.

Anyone here using candlestick or wall phones with original (not-bulldog) transmitters?

Ralph Meyer in Old-Time Telephones, 2nd Edition, shows  resistance of 229, 323 transmitters is 25-75 ohms and 395, F1 and T1 75-275 ohms. (page 24).  (337 not listed).

The 337 I tested is on a 151AL which has a 143 receiver...usually it is the transmitter that is upgraded so I'm not sure how this combination happened. However, I also tested the same 151AL connected in the correct way to a 302 base (using all 4 leads from the phone), and the sidetone was still very high. That's why I said before that it seemed to be this particular transmitter rather than the sidetone vs. antisidetone circuit.


[Sleep deprived ramblings:

The WR specs were printed on blue stock...unless there was a shortage of blue dye as well??? (Lucky Strike cigarettes changed the color of their packaging to red: "Lucky Strike Green has gone to war.")

My scanner is currently giving an unable-to-connect error message, even though I am able to print or copy. Perhaps the fax function is OK?...assuming you have a real telephone line to receive it...If alarm systems, dialup modems and fax machines won't work with VOIP, are the fire departments/building inspectors changing their requirement for two land lines (one must be dedicated and one can be shared with other voice terminals thru an RJ31X jack) for smoke/fire alarms? Was Elisha Gray right after all, along with all the others who were looking for pulsing rather than analog transmission of speech?]
"C'est pas une restauration, c'est une rénovation."--François Martin.

Offline poplar1

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Re: Connecting a 51AL to a 684A (or 634A or 302 base)
« Reply #8 on: October 09, 2013, 02:19:30 PM »
See Figure 1--51AL Sidetone Desk Stand For Sidetone Service (Manual and Dial)  [while using an anti-sidetone subset]. This is the one that no longer appeared in the 1946 addendum.

Again, the reason I think this circuit is useful is that

(1) Sidetone Subsets are becoming difficult to find because most, if they survived, were converted to anti-sidetone. Also, 302 bases are readily available for making anti-sidetone subsets.

(2) It is not practical to convert a sidetone desk stand (20AL or 51AL) to anti-sidetone (120AL or 151AL) at home because it would involve adding additional contact springs and additional wiring. In fact, this way, the original wiring of the set stays the same. The only wiring changes are minor ones in the subset or 302 base.

(3) If you want to use an existing 3-conductor cord on a 102 you can do so. Otherwise, you would need to add a 4th conductor to use an AST subset in the usual configuration.

(4) As with any sidetone subset circuit, you can connect multiple phones to one subset. You just need to extend triple wire (red, green and yellow) from the output of the subset to each phone. I have seen old apartments wired this way: triple inside wire (Tip, Ring and Ground) from the basement to a metal 534A subset in the hall of each apartment. Then one or more phones connected to R, GN and L2Y of the one subset. (I currently have two 51ALs connected to one 302 base wired as in Figure 1.) The main phone in the hall would connected directly to the subset, while the extensions would be connected by means of triple inside wire which connected the subset to  baseboard connecting blocks in the living room or bedrooms.

While the capsule transmitter unit (F1) starting around 1935 and the anti-sidetone circuit starting around 1931 were definitely improvements, still, the disadvantage was that instead of one sidetone subset for all sidetone desk stands (20AL etc) and hand telephone sets (102 etc) in the entire residence, each anti-sidetone phone (151AL, 202) now required its own anti-sidetone subset, even though you could opt for some subsets without ringers (684-C?).

While there were special phones with extra contacts needed where more than one desk stand or hand telephone set was connected to one anti-sidetone subset, these phones are rarely seen: 151R desk stand, 215 (D-8) hand telephone set, 213 "space saver." These sets open the red lead from the subset; otherwise, both transmitters are connected even if only one phone is off-hook.
« Last Edit: October 09, 2013, 02:44:14 PM by poplar1 »
"C'est pas une restauration, c'est une rénovation."--François Martin.

Offline poplar1

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Re: Connecting a 51AL to a 684A
« Reply #9 on: October 09, 2013, 02:25:29 PM »
WR-C63.373--See top diagram
« Last Edit: October 09, 2013, 02:27:24 PM by poplar1 »
"C'est pas une restauration, c'est une rénovation."--François Martin.

unbeldi

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Re: Connecting a 51AL to a 684A
« Reply #10 on: October 09, 2013, 05:30:10 PM »
WR-C63.373--See top diagram
Thanks much for the scans or pictures, not sure which process you used, came out great without removing the pages from the binder.  I processed the images just a little bit to clean up, cropping etc... result is attached.

The date of the document is 9-30-42?
Which date/Issue do you have of the standard C63.373? The only one I have found is Issue 2 of 1937 and since  the quoted addendum is for 1946, I assume there were no other revisions between 37 and 46?

unbeldi

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Re: Connecting a 51AL to a 684A (or 634A or 302 base)
« Reply #11 on: October 09, 2013, 05:48:33 PM »
See Figure 1--51AL Sidetone Desk Stand For Sidetone Service (Manual and Dial)  [while using an anti-sidetone subset]. This is the one that no longer appeared in the 1946 addendum.
One certainly has to wonder why they removed it later, while retaining a circuit that has clear electrical deficiencies (loading the line heavily).

Quote
(2) It is not practical to convert a sidetone desk stand (20AL or 51AL) to anti-sidetone (120AL or 151AL) at home because it would involve adding additional contact springs and additional wiring. In fact, this way, the original wiring of the set stays the same. The only wiring changes are minor ones in the subset or 302 base.
And it does not appear useful today today to undertake such conversions, unless someone insists on using a candlestick for everyday telephone use.  For collection purposes they should be displayed and played with in their original beauty. It is very cool to show someone what sidetone actually is and how such telephones sounded, rather than to show someone that you figured out a way to get rid of it.


Quote
(4) As with any sidetone subset circuit, you can connect multiple phones to one subset. You just need to extend triple wire (red, green and yellow) from the output of the subset to each phone.
This is the feature that is very friendly to today's collectors and that probably few know about. There is no need to come up with many subsets in a larger collection and still remain authentic. I am glad you pointed it out.

Scanning eBay, it is clear that it is rather difficult to find an original, e.g., 534A that hasn't had its original coil exchanged.
« Last Edit: October 09, 2013, 06:03:48 PM by unbeldi »

Offline poplar1

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Re: Connecting a 51AL to a 684A
« Reply #12 on: October 09, 2013, 09:45:05 PM »
About the only way to find an "original" WE metal 534A subset on ebay---is to build it yourself!"

1. Start with a 634A.

2. Find a junker 533A wall phone--broken receiver, bent cover, missing transmitter unit, whatever--that still has the original 46-type induction coil (wood ends).

3. Swap covers.

The code number on the back, if present,  will be wrong--533A instead of 534A--but once mounted on the backboard this won't be visible.
"C'est pas une restauration, c'est une rénovation."--François Martin.

unbeldi

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Re: Connecting a 51AL to a 684A
« Reply #13 on: October 09, 2013, 11:01:47 PM »
About the only way to find an "original" WE metal 534A subset on ebay---is to build it yourself!"

Well, you can. About a year ago I found a set of two original 534A  via someone in small place in western Nebraska (Hastings) .... on Ebay!  I have seen just a few since in the same original condition.

 
« Last Edit: October 10, 2013, 03:13:49 AM by unbeldi »

Offline poplar1

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Re: Connecting a 51AL to a 684A
« Reply #14 on: October 10, 2013, 09:48:40 AM »
WR-C63.373--See top diagram
Thanks much for the scans or pictures, not sure which process you used, came out great without removing the pages from the binder.  I processed the images just a little bit to clean up, cropping etc... result is attached.

The date of the document is 9-30-42?
Which date/Issue do you have of the standard C63.373? The only one I have found is Issue 2 of 1937 and since  the quoted addendum is for 1946, I assume there were no other revisions between 37 and 46?


The only issue of the regular practice I have seen is Issue 2, 3-1-37. (Paul--is there a list somewhere of extant issues????). The WR section I scanned is 9-30-42.
"C'est pas une restauration, c'est une rénovation."--François Martin.