Transmitter element for 1A interphone

[JimHyak]

There is an amazing amount of knowledge among the members of this forum, it never ceases to amaze me! Although I collected as a kid, I only really got back to it recently. Since I've never worked in the business, sometimes learning about something is tough. I have become interested in the 1A interphone. Can anyone tell me the difference between a N1 transmitter element and a N2?
Every interphone I've seen uses a N2 as a mic element in the phone, i.e. a 659A transmitter for the 558 wall phone will use an N2 transmitter cartridge and a resistor divider and cap. Every operator headset mic I've opened so far has a N1. Mechanically the same, but what about electrically? I see different generations of U1 Rx elements used interchangeably in handsets (U2, U3, etc.) but only the U1 as a mic for the 730A Door Phone, don't really know the difference there either. And, if one of you can whip out a BSP reference about this, how in the heck do you do that??

Thanks for all of you that answer the questions on this forum, Jim

[poplar1]

Many U-1 receivers were restamped U-3 at the WE Service Center when the old metal varistors were removed and new varistors were installed on them. So that is probably the only difference in U-1 and U-3. Of course, newer receivers with the green varistors were designated U-3 from the time of manufacture.

[paul-f]

And, if one of you can whip out a BSP reference about this, how in the heck do you do that??

See page 3 here:

http://www.telephonecollectors.info/index.php/document-repository/doc_details/2713-501-230-100-i8-transmitters-and-transmitter-units-id-and-maint-tl

http://www.telephonecollectors.info/index.php/document-repository/doc_view/2713-501-230-100-i8-transmitters-and-transmitter-units-id-and-maint-tl

Found by searching for "n2 transmitter" using the Google Site Search from the menu on the TCI LIbrary home page:

   http://www.telephonecollectors.info

There are also several references found by searching using the standard search for "1A interphone."

Edit: Alternate link added.

[JimHyak]

Paul
Thanks for the help. Bummer that that I can't just take a N1 from a headset and use it as a interphone transmitter. "Reduced carbon fill" Hmm, sounds like a challenge for a future time.

The TCI site is great, but I'm still getting the hang of navigating it. Seems I should join and send them some money.

Your site was one of the first I found when i came back to collecting, what a reference it has become, I love it and use it all the time. I feel I should be supporting it as well!

[paul-f]

You're welcome, Jim.

Just because the Bell System wouldn't use an N1 doesn't mean it's not worth a try.

You can always leave a donation to TCI using the donate button on the Library site.  Of course, joining would be a better first step.

I keep meaning to add a donate button to my site.  Contributions are always welcome.