Cortelco compact ringers for 500/2500 series

[dsk]

The best picture i can find is this:
I am so impressed of how simple it is possible to build a well working ringer.  It is so compact, and does still have 2 gongs low REN load, and has even adjustable volume.

Why none has done it before, a U shaped core with winding, and a rolling steel ball kept in position of a permanent magnet in the middle. 

Anybody with some experience from these, good or bad?

dsk

[dsk]

I tried to draw up on the photo how it works.

dsk

[twocvbloke]

My Cortelco 2554 has a similar ringer, but a single-gong version, it works, but it just sounds a bit odd as the ball bearing is hitting the gong for too long unlike a traditional clapper which just taps it allowing it to ring in the way that they do, it's definitely a much simpler and cheaper way to have a traditional mechanical ringer, but just doesn't have the right ring to it...

On a similar note, my Geemarc "Mayfair" lookalike of a GPO 746 has a 2-gong copy of the Cortelco ringer, and it sounds dreadful very poorly copied and the gongs are of similar tones meaning it hasn't quite got the right sound for any telephone, it does work though, and rings quite loudly, but, the gong notes don't sound right at all...

http://www.classicrotaryphones.com/forum/index.php?topic=11573.msg123522#msg123522

[dsk]

That is most interesting, the rest time on the gong may depend on the frequency, and the diameter of the gong, maybe even the distance from the poles on the u shaped magnet. It seems like it is impossible to adjust. It could be worth a try to test another size ball bearing ball. I will guess it should be bigger at lower frequencies. I am not sure but I will guess this is ringing at almost every frequency between 15 and 60 Hz, but is optimized for something in the middle.

dsk

[dsk]

Not easy to test at different frequencies, but here you may hear mine at 25Hz and 20Hz One ring of each: http://tinyurl.com/mev2uhb

dsk

[mentalstampede]

I have a manual 554 with one of these ringers. I've been impressed with how well it works considering how much simpler it is.

[unbeldi]

Straight-line ringers of the WECo C-type generally are designed to work from ca. 15 Hz to perhaps 35 Hz max. Outside that range, both on the low side and the high side, the impedance rises drastically to values where not enough energy (current) is available to strike the gong effectively.

The FCC defines them as responding from 15.3 Hz to 34 Hz, but they also define a B-type ringer for any frequency (15.3 Hz to 68 Hz), but I suspect this is not an electromechanical ringer.