Western Electric 20AL to 584A Subset

[Logan1]

I have a Western Electric 20AL candle stick phone that I am trying to hook to a 584A subset to. It has a filter and 3 wires from the phone to subset. So far it rings out and takes calls but the ringer in the subset does not ring, also the volume is real low, hard to here on both ends, some thing is not wired right. Can anybody help.

[unbeldi]

I have a Western Electric 20AL candle stick phone that I am trying to hook to a 584A subset to. It has a filter and 3 wires from the phone to subset. So far it rings out and takes calls but the ringer in the subset does not ring, also the volume is real low, hard to here on both ends, some thing is not wired right. Can anybody help.

What do you mean by "It rings out"?  How can it do that, if we take that literally.

The 584A subset from the factory had only one capacitor, a 149A (1MF), so you have to be particular how you connect the ringer to a line with dial tone and DC loop current. This may be your problem.

The connection of a 20AL to a sidetone subset (534A, 584A) is covered in BSP C63.373 Issue 2 of 1937, entitled ''Desk Stand Connections", for example, there are probably other places too.

The first page of the BSP is all you need, it has the diagram, the other three pages cover other stands.

This diagram shows an optional tube in the ringer circuit, which you probably don't have, so connect the ringer leads straight between L1 and the C terminal, for a 'modern' line.


PS:  I removed the images originally posted for manual desk stand, and crossed out some content above, to avoid confusion.

[unbeldi]

Oops.  Looking at your actual pictures now, it seems you don't have a 20AL desk stand at all.  The 20AL is a manual stand, yours has a dial.....   reboot.


You need the diagram for a 50AL or 51AL.

[unbeldi]

Oops.  Looking at your actual pictures now, it seems you don't have a 20AL desk stand at all.  The 20AL is a manual stand, yours has a dial.....   reboot.


You need the diagram for a 50AL or 51AL.

Ok, so here is the entire BSP, look for figure 3 for the 51AL.  These diagrams also include the filter connections.

[Logan1]

I have 3 wires from phone to subset, the ringer wires are , black to C and redish wire to L1.      I for got to say it had a dial.

[unbeldi]

I have 3 wires from phone to subset, the ringer wires are , black to C and redish wire to L1.      I for got to say it had a dial.

Your stand is a 51AL, since it has the connection plates inside.
It seems one of the condenser leads (I am guessing, because I can't see where it is going, but it is logically the only choice) is connected to the ground terminal on the coil, instead of L2Y. Move the wire, and it should ring, if the condenser is ok.  This should also enable the functioning of the secondary winding of the induction coil.  The condenser should be between C and L2Y.

What you want is a bridged ringing configuration, where the ringing signal comes from Tip and Ring.

[Logan1]

I took the wire off GND and put it on L2Y and it rinds but when I lift the receiver off and set back on the hook the bell dings. And when I call the stick phone I can here myself  in the receiver. I do not know why it would do that, and ding after hanging up the receiver.

[Logan1]

I here an echo in the receiver of the candle stick phone when I hold it to my ear and talk.

[Logan1]

Every time I lift the receiver hook and put it back the bell will ding one time, but it rings now.  What is the filter for ,is it needed, I can here myself in the receiver of the candle stick phone, not right.  Thanks

[unbeldi]

Well, congratulations!  This is what the state of technology indeed was in the 20s and early 1930s.

What you are hearing is called sidetone.   It is essentially an electrical feedback from the transmitter to the receiver.  You are having an authentic 1920s user experience.

For this reason, engineers worked for almost 10 years to perfect an electrical circuit called the anti-sidetone telephone circuit (AST).  Essentially the solution was to add a third winding to the induction coil, which is used in the circuit such that it cancels the sidetone.  But it does not completely cancel it, because some sidetone is necessary to assure the human nature that the device is actually working. When people can't hear themselves they raise their voice.  Musicians on stage have speakers in front of them to produce sidetone directed at them, because they can't hear themselves from the speakers directed toward the audience.

Western Electric's anti-sidetone subset came out in 1931, about a year after the 584A was introduced.  Many 584A subsets were later converted to 684A, the model number is always +100.   Some modifications were also needed in the desk stands, and those were also renumbered, a 51AL became a 151AL.  The stand needed an extra hookswitch contact and the wiring was more complex. The mounting cord to the subset was now a four-conductor cord.
The subsets needed a second condenser, because the audio circuit was now separate from the ringing circuit.

[Logan1]

Amazing, why would the bell ring one time when I mover the hook up and down,  I have a 685A and a 302 base, would one of those work better if I wanted to change later.  Thanks

[unbeldi]

Every time I lift the receiver hook and put it back the bell will ding one time, but it rings now.  What is the filter for ,is it needed, I can here myself in the receiver of the candle stick phone, not right.  Thanks

Every time you take the set off-hook, current starts flowing through the local loop, and for a very short amount of time the capacitor allows current to flow while it is charging up, therefore the magnet is energized for a moment and the armature swings out, and you hear the bell.  This was annoying of course, and the solution was to put a little tension on the armature of the ringer, to keep it on one side.  It's called a bias spring, and the ringer is called a biased ringer.   Please check to see if your ringer still has it.  They do often get lost, because the thin thread deteriorates.  The ringer has a screw adjustment to set the tension on the spring, and therefore the amount of bias. If your set still has the spring, you can try to increase the tension just enough to stop the ring.

The filter is to suppress radio interference during dialing.  When the DC loop current is interrupted by the dial, electromagnetic pulses of high frequency are generated and those would be picked up by old AM radios of the time and you could hear the dialing in the radio.  The filter eliminates the high frequencies.

[unbeldi]

Yes, the picture does show a spring, but I can't tell its tension.  You can experiment with that.

[Logan1]

Yes it has the spring I will check it out tomorrow .  Thanks for your help.

[unbeldi]

Engineers worked on the anti-sidetone circuit for actually a lot longer that 10 years, as I mentioned.  The origins of the idea were laid in the first few years of the century.  A key figure was G.A. Campbell at AT&T, who laid the mathematical foundation of loading coils and networks, as well as many other concepts.

The commercial success of the anti-sidetone circuit was not only an electrical solution, but a development of several improvements that happened simultaneously and culminated in the E1 handset that was used on the successor telephone after the candlesticks. This also included the non-positional transmitter. These components needed to be tuned to each other electrically as well as mechanically, and not all matured at the same time.  It appears that the electrical circuitry was actually settled last, and that would make logical sense as the other components needed to be characterized in terms of electrical and acoustic gain and loss, first, before the proper dimensioning of the AST balancing circuit.

The desk stands were revamped for AST as well, and converted to the 150 and 151 types.  Since your desk stand clearly is intended to be a 51AL, I would really leave it as is.  You couldn't have a more authentic and historic piece and experience, and a very nice demonstration for friends and family.
If you do actually want to use the set much, I would start looking for a real 151AL with a 684A subset. The experience will be similar to a 202 or 302, depending on the type of receiver and transmitter elements in the set.