Northern No. 1 Mahogany Brown

[Jack Ryan]

Certainly correct, Jack.

At the minimum of the impedance vs. frequency graph, i.e. where the current is the largest as described, the capacitive reactance of the ringing capacitor cancels the inductive reactance of the ringer and the imaginary part of the impedance is zero, it's purely real.

Yes, it's unreal isn't it!

Jack

[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.

Returning to the discussion of the ringer of this Uniphone....   Last week I spent some time looking at the early B-type ringers that WECo produced before product launch in 1937.  You can find enough information even from the many 302 dev sets that are shown in pictures on the forum.

It appears that one of the ringer types tested in the 302 field trials of 1936 had the identical blade spring armature mount as the ringer in this Uniphone.  Now, Western Electric didn't have any reason to field-test frequency ringers, they hadn't used them anymore in 20 years.  Since the ringer also has a bias spring, I have no doubt anymore that this is in fact not a frequency-selective ringer, but a straight line ringer.

The reason for this type of armature mount is unclear of course, but perhaps they were trying to eliminate the mechanical friction and wear of metal-metal contact of the axle or set screw.  They did so finally in the C-type ringer of the 500-set, which only has a flexible reed spring and no friction.

In a private discussion with Jeff, we agreed that Northern Electric probably bought these ringers and the induction coils for the first Uniphones from Western Electric, rather than making their own. There was pressure in the market place to compete with the combined telephones of the independent makers, and NECo didn't want to loose that business by waiting for the completion of the 302,  a situation that was different for Bell Canada, which decided to wait, but which also had a more captive market than the independent telephone companies.

[wds]

Excellent information - thanks.  For the fun of it, here are pictures of the back of the dial. 

[unbeldi]

Excellent information - thanks.  For the fun of it, here are pictures of the back of the dial.

Looks like a No. 10 GPO dial.
Here is a link for a maintenance guide of 1938:  http://www.britishtelephones.com/tel%20auto%20b5126.htm