1907 Ringer Box

Thread Starter

Nidraclark

Joined Jun 15, 2014
2
Hello Everyone,

I picked up a early's 1900's ringer box at a yard sale today for $10 and am hoping to get some help increasing my understanding of how it works. I assume it's function is similar to a tattoo guns where the two coils act as electromagnets. I guess my main question is the purpose of the 2mF Cap and the larger inductor(?) shown in the image.

Thanks
 

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Dodgydave

Joined Jun 22, 2012
9,157
The capacitor is to let the pulsed DC for the ringer to operate when receiving a call, once the phone has been answered the exchange switches to steady DC to communicate the audio, so the cap blocks it out so the ringer wont operate during a call.
 

Thread Starter

Nidraclark

Joined Jun 15, 2014
2
Thanks everyone for the replies I had to replace some wiring but it is now works as a ringer. When reading up on the ringer I saw a posting that addressed the possibility of rendering the ringer useless if you remove the permanent magnet the is behind the inductors. Can anyone suggest some online literature regarding the effect of permanent magnets on the induced magnetic field of induction coils?
 

#12

Joined Nov 30, 2010
18,210
The tiny bit that I know is that ring frequencies were about 20 Hz to 50 Hz and the capacitor is used to make a resonant circuit at the frequency of that particular ringer.
 

cbenham

Joined Dec 18, 2013
1
The tiny bit that I know is that ring frequencies were about 20 Hz to 50 Hz and the capacitor is used to make a resonant circuit at the frequency of that particular ringer.
You are right but here is some more detail... The frequencies used for 'harmonic ringing' are 20, 33, 42, 54, and 66 Hz. At leaet they were in the early 1970s when I worked for General Telephone in Florida. The ringers had different size weighted clappers that were held in place with a set screw
which allowed a technician to tune the mechanical resonance of the bell unit.

I think today harmonic ringing is gone since there are very few if any party lines in use.
 

inwo

Joined Nov 7, 2013
2,419
The permanent magnet is used to bias the ringer to center. It helps to keep line noise from dinging the bell. As memory serves.

A little known fact. I'm almost single handedly responsible for the rarity of old phones.

I destroyed countless phones in the 50s. (we just switched over then).
Beautiful quarter sawn oak cabinets destroyed so I could play with their innards.:eek:

Then in the 60s, I did the same with console radios.

stupid stupid stupid!!!
 

EinarA

Joined Sep 13, 2014
5
The magnets are essential for the operation of the ringer. Since iron is attracted to either polarization of electromagnetism the clapper will not move from side to side with an AC signal. With a permanent magnet added, one coil will have an increasing field while the other decreases for one half cycle and the opposite for the other half cycle. This makes the clapper move back and forth, striking each bell once a cycle.
A capacitor must be placed in series with the electromagnets because a DC load on the line is sensed as an "off hook "condition. The pictured ringer apparently uses a series resonant circuit as well, but in most POTs the inductance and capacitance are too small to resonate at the ring frequency.
 

alfacliff

Joined Dec 13, 2013
2,458
the ringer isnt very much like a tatoo gun, the tatoo gun has a set of contacts that alow dc to make the armature buzz. when pulled in, the points open and the armature drops out, closing the contacts again. the ringer is operated by an ac signal, and needs no contact points.
 
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