Using an Automatic Electric 50 with my building intercom system

[jvennema]

Hi Guys!

I'm new to this world, moderately technically ambitious, and also pretty technically deficient, so that's my caveat for all this moving forward. Also, I apologize in advance for the length of this post. It probably has a lot of unnecessary detail.

I recently remodeled my prewar New York apartment and have put a lot of effort into maintaining the charming, classic character of the place. The cheap, white plastic phone I'm using for my intercom feels like a sore thumb to me, so I got what I now understand to be an AE50 wall phone. Not contemporary to the 1923 construction date, but sufficiently deco to feel in character. Its great, I really love it. The person from whom I purchased it appears to be a refurbisher of antique phones and avowed that it was in proper working order, and I have no reason to suspect that is/was not true.

The building intercom has no complicated features. I literally only need to be able to dial "0" to reach the front desk. The front desk needs to be able to call up and talk to me. That's it. The intercom is wired with regular phone wire and we are told to use regular phones with it. But of course I have struggled mightily to get my AE50 to work.

I have not yet been able to get anyone who can get me technical details of the intercom system itself, so I'm still working on that, but I have pretty conclusively determined that the system requires DTMF tones. My cheapo modern wall phone has a switch for pulse tones, and will not call out when its in pulse mode.

Hoping to keep the unit complete in its case, I ordered a rotatone, assuming that once the old phone generated a DTMF "0" I'd be good to go. I then proceeded to tear my hair out trying to wire it properly.

Eventually settling into using this schematic (http://www.oldphoneworks.com/files/oldphoneguy/rotatone/rotatone-ae40.pdf) for an AE40, which I understand to be substantially if note entirely similar, I have wired in my rotatone.

The one notable distinction between this diagram and my phone is the "cap", which is not a component of my AE50. Instead it has two condensers, 1mf and 4mf (for the record I have no clue what these do or what those measurements mean). In relation to this schematic, I have wired it such that wires run from "BR/W" to "BLK" through the 4mf condenser, and from "BR" to "GN" through the 1mf condenser.

And... success! My phone now generates (what sound to me like) correct DTMF tones when I dial. Hooray!

Except it still doesn't break dial tone or actually call out. Having given it my first, best shot, I'm hoping someone here might have thoughts on how I can about troubleshooting this project.

Some notes and things I've thought about here:

• The original resistor, which is between the hook and the new zener diode, broke, or finished breaking, as I was fiddling around. It appears to literally be filament wire wrapped around a plastic spool; the spool broke on one end which broke the tiny little connection between one end of the filament and the soldered wire end. I replaced it with a 100ohm resistor from an electrical hobby store, which I soldered inline. The original circuit diagram, which is nearly illegible, appears to annotate something like "100^uu" which I figured maybe means 100 ohm? Maybe that's a "w" which used to mean ohms, according to the internet? Even under a microscope I can't really make out the superscript. I could potentially repair the original resistor, although it is extremely fiddly and the connection is nearly microscopic.
  
  
• -The dial tone as it currently exists sounds somewhat "dirty" to me. There's the regular tone, and what sounds like a more electronic overtone. My crappy modern phone has a much "cleaner" sounding dial tone. I have yet to revert the wiring of the AE50 to the original configuration to see if this changes the character of the dialtone, so that's probably something I should do.
  
  
• -When I use a tone generator on my cell, nice and loud, to play a "0" tone through the mic of the AE50 as currently wired, it STILL will not break dial tone or dial out. This method works fine with my crappy modern phone. If I revert the wiring to the original specs I will see if this method dials out on the AE50, which would probably be useful to know.
  
  
• -I have not gone through and cleaned contacts, or re-soldered contacts that seem worn. I am reluctant to do so for fear of putting undue stress on any more fiddly connections. But perhaps this is a thing I really should be doing?
  
  
• -I don't believe I need the polarity guard given that I believe the polarity is correct and the use case here is pretty specific. It might be better to lose it and reduce potential problem sources, but I'm not confident in my ability to adjust the wiring diagram to remove it.
  
  
• -My working theory is that extra line noise being generated by the phone is enough to distort the DTMF tone such that the (probably itself pretty antiquated) intercom system can't recognize it. I don't know if that is or can be caused by my having miswired/dirty contacts/something else.
  
  
• -I can receive calls and speak to the front desk. However, the phone does not seem to ring when the front desk calls up. I believe there is a very faint "buzzing" when they call, and when I pick up the phone when I have asked them to call up I can talk, but it doesn't seem to be engaging the ringer. I though this was mechanical due to the phone being on its back, but I propped it up and no luck.
  
  
• -After wiring the phone with the rotatone the bell now rings once when I hang up the receiver. It appears to happen when the hook switch contacts are semi-engaged, mid-way through being hung up, and stops when they fully break the connection. So I know the bell works in some form or fashion! Just not when I want it to.

So that's my little saga. I'm going to work on posting some photos and maybe a .wav link of the dial tone. Any thoughts on some productive things to explore or change would be greatly appreciated!

Cheers,



John

[TelePlay]

John,

Welcome to the forum.

I'm sure other more familiar with your equipment will help you. However, they will ask for pictures so if you could post them, that would be appreciated.

[.....]

Welcome to CRPF.