Straight Line Ringers vs. Harmonic Ringers

[poplar1]

For most applications, straight line ringers are preferable to harmonic ringers. Straight line ringers will respond to a range of frequencies including 20~ (Hertz or Cycles per Second), 25~ and 30~. Traditional telephone lines are 20~. Many key systems use 30~. The Panasonic 616 Key System uses 25~.20~

Many of the phones made by Automatic Electric, North Electric, Stromberg-Carlson and Kellogg have harmonic ringers. These were used on multi-party lines. This permitted selective ringing of each party. The central office sent a specific frequency of Alternating Current (AC) depending on the party dialed--16~, 33~, 50~, 66~, etc. Only the intended party's phone would ring. Other ringers on the line would not respond to another party's frequency.

If your AE 40, AE 50, Kellogg 1000 ("Red Bar"), Stromberg-Carlson 1212 ("Fat Boy"), etc., won't ring, you may have a harmonic ringer. If so, and its frequency doesn't match the frequency of your ringing source, it won't respond or will barely move. While it is possible to practice "surgery" on these with more or less success, it is usually preferable to start out with a straight line ringer.

Straight line ringers, except those used on magneto lines (think hand generators), usually have a biasing spring. This prevents "tinkle" or bell taps when dialing and when going on- or off-hook. Harmonic ringers don't have biasing springs, but are often recognizable by the brass weight on the clapper assembly.

[poplar1]

Kellogg straight line ringer and harmonic ringer:

[poplar1]

Automatic Electric Straight Line Ringers

[poplar1]

Automatic Electric harmonic ringers:

[Dennis Markham]

Nice informative post, poplar1.  Thanks.

[HarrySmith]

Thanks for taking the time to post those great comparison photos

The one thing I have always used if I cannot read the numbers, is that the frequency ringers have adjustable clappers. I have never seen an adjustable clapper on a straight line ringer.

[Phonesrfun]

Thanks for taking the time to post those great comparison photos

The one thing I have always used if I cannot read the numbers, is that the frequency ringers have adjustable clappers. I have never seen an adjustable clapper on a straight line ringer.

For me, I look for the pivot on the armature for a straight-line ringer.  The rigid tuned reed of a frequency ringer is not pivotal.  The sometimes large, and usually adjustable clapper weight is, like you say, a good way to identify the frequency ringer.

[Greg G.]

Good info!  You answered a question I was thinking of posting here, even though I think I already knew the answer - Can frequency/harmonic ringers be modified to work on modern phone lines.  Answer is pretty much no, not worth the hassle.

[Phonesrfun]

I have never had the patience to screw around with trying to make one work that is way off in frequency.  For instance I would rather go find a straight line ringer if I had a frequency ringer that was rated at 66.6667 ~.  It's just too much hassle to work with.

On the other hand, I have gotten acceptable results with a 20 ~ frequency ringer on 25 - 30 ~ ringing current, but I must say, I have NEVER gotten a frequency ringer to perform as well as a straight-line ringer.  I think there are just too many variables to work with on most ringers.  Sometimes it becomes a necessity to coax one into working  when a straight-line ringer is not available, or when the cost of one would be prohibitive.  Here are the electrical and physical variables that need to be taken into consideration:

1.  The resonant frequency of the LC circuit formed by the coils and the capacitor.  In my opinion this comes into play, but may not be as important as the next two.
2.  The physical properties of the "reed" that connects the clapper with the armature.  This includes the material it's made of and the stiffness, thickness, springiness, metallic composition, etc.
3.  Closely related to #2 is the weight and the position of the weight that is on the arm, which sets up a resonance with the reed action.

The reed is like a hacksaw blade that vibrates when plucked.

ALL of these things work in close cooperation with each other.

[mentalstampede]

I've been experimenting with a 50 hz ringer on a 20 hz ringing line the past couple days. Changing the capacitor value was absolutely necessary to get any response from the ringer at all.  Depending on the value of the capacitor, the capacitor blocks AC frequencies below a certain cutoff point. In my case, the .08 MF capacitor was blocking almost all AC below approximately 45 hz from even reaching the ringer coils.

Once I had substituted a more appropriate capacitor in the ringer circuit, I was able to get an acceptable ring by tweaking the geometry of the clapper arm and clapper location. I also substituted a couple of soft rubber o-rings in the mounting of the vane instead of the rigid washers. This allows slightly easier movement of the clapper. It does appear to be polarity sensitive, but I can live with that. 

Here's a quick video of it ringing after my modifications: http://youtu.be/LITeUBf_jAE

[Phonesrfun]

.....It does appear to be polarity sensitive, but I can live with that. 

What part makes it appear to be polarity sensitive?  Seems to me that the capacitor in series with the ringer should remove all of the DC line current bias and leave only the AC component of the ringing current.

[mentalstampede]

What part makes it appear to be polarity sensitive?  Seems to me that the capacitor in series with the ringer should remove all of the DC line current bias and leave only the AC component of the ringing current.

I don't know why, but it certainly doesn't remove all of the bias. Connected one way, the clapper rests solidly against one of the bells, and when rung doesn't even move far enough to touch the other bell. That makes for a particularly weak and muffled sounding ring.  But reversing tip and ring causes it to rest equidistant from the bells and strike both. I'm sure DC bias is the reason, but I think I'm going to leave well enough alone on this one.

[Bill]

To bias the ringer position as you describe, the capacitor in your phone must be leaking. In other words, a bit of DC gets through it. This won't hurt the ringer, but eventually it will cause the phone to appear to be "off hook" even when you hang it up. If there is a second section of the capacitor, and if it leaky as well, it will eventually damage the receiver by altering the magnetism.

There are several easy ways to check it, but it depends on what test equipment you have (milliammeter?) or spare parts (another capacitor?)

Bill

[G-Man]

To bias the ringer position as you describe, the capacitor in your phone must be leaking. In other words, a bit of DC gets through it. This won't hurt the ringer, but eventually it will cause the phone to appear to be "off hook" even when you hang it up. If there is a second section of the capacitor, and if it leaky as well, it will eventually damage the receiver by altering the magnetism.

There are several easy ways to check it, but it depends on what test equipment you have (milliammeter?) or spare parts (another capacitor?)

Bill

Bill is right on the money since the capacitor should block all dc. Another factor may be that the replacement capacitor is not non-polarized and/or it does not have a sufficient breakdown voltage rating.

[mentalstampede]

To bias the ringer position as you describe, the capacitor in your phone must be leaking. In other words, a bit of DC gets through it. This won't hurt the ringer, but eventually it will cause the phone to appear to be "off hook" even when you hang it up. If there is a second section of the capacitor, and if it leaky as well, it will eventually damage the receiver by altering the magnetism.

There are several easy ways to check it, but it depends on what test equipment you have (milliammeter?) or spare parts (another capacitor?)

Bill

Thanks! The capacitor came out of a spare/used parts bin, so that's probably the cause.  I have access to plenty of equipment, but it sounds like trying a different capacitor is probably the way to go.