Northern No. 1 Mahogany Brown

[Ktownphoneco]

That certainly improves my understanding of ringers.        I can't understand why the NB1A has a bias spring either.     But with a spring steel armature pivot, would it not have been tuned to operate within a particular frequency range in order to operate efficiently ?      Yes, I think the Northern N3A condenser was most likely a copy of Western's 194.
I pulled the date 1937 out of Ralph Meyer's book.    I knew the 101-A coils predated the Uniphones, but I didn't realize they went back that far.

I've added a better (but not perfect) picture of the NB1A ringer showing the armature spring pivot.

Jeff

[wds]

When I manually move the clapper from side to side, it feels like a normal ringer, not a frequency ringer.  It moves side to side likes it's on a pivot.  I will take a closer look  tonight.

[unbeldi]

That certainly improves my understanding of ringers.        I can't understand why the NB1A has a bias spring either.     But with a spring steel armature pivot, would it not have been tuned to operate within a particular frequency range in order to operate efficiently ?      Yes, I think the Northern N3A condenser was most likely a copy of Western's 194.
I pulled the date 1937 out of Ralph Meyer's book.    I knew the 101-A coils predated the Uniphones, but I didn't realize they went back that far.

I've added a better (but not perfect) picture of the NB1A ringer showing the armature spring pivot.

Jeff

The History of Engineering and Science in the Bell System (The Early Years), mentions the 101 induction coil as 1930 vintage.   But except for the development versions of the 302 we don't see the 101A used in early subsets for some reason before the 1935 catalog.  The 1931 anti-sidetone BSP informally announced it also (C31.111 i1 1931-06-01 Anti-Sidetone Subscriber Sets...):
    The subscriber set codes listed in the tables cover the
later type condensers, dials, induction coils, etc. Where
equivalent condensers, dials, induction coils, etc., of older types
are available, they may be used in place of those listed. In
this connection a new type closed core induction coil (101 type)
will be furnished in some new sets.

More prominently, the 101A induction coil is first defined in 1933. (C31.401 i1 1933-11-22 Induction Coils; Description and Use).

There was apparently great hesitation for introducing the anti-sidetone circuit in the field.  Partly of cost it seems, because technically the circuits had been well established for some time. With the recession of 1933, fewer telephones were newly installed than existing services disconnected, so it was probably a lot cheaper to add another winding on top of existing No. 46 and No. 13 induction coils, to make a 146 or 113, than to make new coils in large quantities.


The electrical tuning of the ringer circuit in frequency ringers is usually by using a suitable capacitor.  This creates an RLC resonance circuit (resistance-inductance-capacitance) in which the ringing capacitor typically varies from 500 nF (1/2 µF) down to perhaps 50 nF, but usually also required increasingly higher ringing voltages because of the inevitably increasing impedance of the ringer coils with frequency.

[unbeldi]

When I manually move the clapper from side to side, it feels like a normal ringer, not a frequency ringer.  It moves side to side likes it's on a pivot.  I will take a closer look  tonight.

If it's that easy it probably is a low frequency ringer.  The higher the frequency, the stiffer the movement.  Since there is no special capacitor on that board for just the ringer, it probably runs at normal frequency.

[unbeldi]

      Yes, I think the Northern N3A condenser was most likely a copy of Western's 194.

I can't find any N3 condensers in the NECo catalogs of the 1930s.  It must be earlier, the replacement of it seems to be the NE-5D, which was replaced by the NE-149A, but that is only a single capacitor canister.
The 194 type has two capacitors.

[Ktownphoneco]

Thanks Karl for taking the time to explain all of the information contained in your reply's.   

Jeff

[Ktownphoneco]

I couldn't find any catalog reference to it either.      I quoted the number N3A directly off the tin canister itself.    I think I still have one in a Uniphone of approximately the same vintage as Dave's set.   
When I get a minute, I'll pull it out of the display case, open it up and photograph the condenser.

Jeff

[wds]

Here's the back of the ringer - I didn't see these markings before.  I looked all over and didn't see anything indicating the frequency.  The clapper definitely pivots on the flat metal spring.

[wds]

Here's the markings on the condenser.

[unbeldi]

Here's the back of the ringer - I didn't see these markings before.  I looked all over and didn't see anything indicating the frequency.  The clapper definitely pivots on the flat metal spring.

Nice, thanks.  Do you have an ohmmeter to measure the DC resistance?  It would be interesting to find out if it indeed has 6000 Ω as Jeff reported.

Interesting that they quote some patent of 1925.

[unbeldi]

Here's the markings on the condenser.

Thanks again, wonderful.

So the N3A is the predecessor to the 194B with 0.5 µF and 2 µF.

[unbeldi]

Thanks Karl for taking the time to explain all of the information contained in your reply's.   

Jeff

You're welcome..... 

We have  a picture, thanks, hope you caught this in time.

[unbeldi]

Here's the markings on the condenser.

Does the induction coil have a patent date on it too?  Lack of that might indicate that it was indeed a requisition from Western Electric.   Here is how a WECo coil was stamped in early 1937.  I think by the second or third quarter they changed to the new style.

[wds]

Couple more pictures of the coil.  Could not find a patent date.  I tested the ringer - my ohm meter is not very acurate, the old needle style.  Registered about 6500 ohms.

[Ktownphoneco]

As Dave has stated, no patent dates visible.    Attached are comparison photos of a Western 101-A and a Northern 101-A, with the only two differences I can find.     Pictures are labeled.
If it turned out that Western shipped Northern the coils, it wouldn't surprise me.

Jeff