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Setting up a home rotary phone network/switching system

Started by briantroutman, February 13, 2018, 02:42:35 PM

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Sorry Greg...I've always had this tendency to confuse yourself and Bill (PhonesRfun) with each other...not in person, just online. No idea why...I associate the two of you together since you both are here on CRPF, both in Washington, both worked on WA shows, met you both at WA shows. Then my error likely threw Brian ... let me check....yup, threw Brian off track.

My apologies and I only wish I could guarantee it won't happen again!



Yes, sorry Greg! I wanted to thank people by name where possible—always feel a little awkward addressing people by screen names. Thanks again for your input and advice.

Quote from: AE_Collector on February 17, 2018, 12:33:57 AM
Any 1A1 or 1A2 System isn’t “really” what you want. ...An add on that a complete key system frequently had was an intercom on a line key to call to other stations.

Thanks, Terry. Based on what I’ve read in the 1A1 system documentation (in the TCI library), it seems that the "Dial Selective Intercommunicating” feature would allow extension-to-extension dialing, but it’s not clear to me whether the key system generates dial tone or an audible ringing signal. It also appears that the Western Electric key systems were sold as a series of modular components, so—if I understand correctly—I would need to find a key system that has the necessary intercommunication module installed in order to dial from extension to extension.

From my perspective, the benefit of using an old Western Electric key system would be having an electromechanical switch connecting the calls. But as mentioned in my first post, I don’t foresee connecting my internal network to an outside phone line (let alone multiple lines), so the added complication of using multi-line desk sets with line selector and hold buttons would make that option somewhat less attractive. You mention that other phones can be modified to work with the that a very complicated process?

And then there’s also some other questions associated with a key system: Where would I find one...and all of the necessary components? How much should it cost? And so on.

Correct me if you disagree, but I think this a fair assessment:
An old 1A1 or 1A2 key system might do what I wanted and have the benefit of using an electromechanical switch (which I’d prefer over an all-electronic system). But still, it would be hard to beat an older Panasonic PBX for availability, affordability, and ease of setup and use.


A dial selective intercomdoes not have a dial tone or ringback


To clarify -

The 1A-series intercoms where you can "dial" a phone, basically have a separate box, which listens for either the tones or counts the pulses, then triggers one line, which you feed with either 90VAC to the bell or 10/18 VAC to a buzzer.  Each phone is punched down to the specific extension it is tied to.  When the appropriate number is dialed, then that "extension" buzzes/rings, but like most 1A-series equipment, the ringing is "out of band", meaning it's done on different wires, rather than the primary line itself.

I'm attaching a basic schematic.  The Icom Box provides a talk path (but no dial tone), when someone "calls" an extension, the box matches the number dialed and passes the VRING and VGND to connections "B" and "G" on the desired device.  B & G are connected to a bell, ringer, etc., based on the input for VRING.  While the extension is "ringing", the calling party hears nothing until the called party answers.  The talk path (T & R) are shared amongst all users.

Valcom (and other manufacturers) make these intercoms, but would require 2-pair to each phone - one for talk, and the other for signaling (plus you'd have to rewire the phones, if they're just single-line phones).

I hope this makes sense...

A phone phanatic since I was less than 2 (thanks to Fisher Price); collector since a teenager; now able to afford to play!
Favorite Phone: Western Electric Trimline - it just feels right holding it up to my face!


In other words, the talk path is there for all switching. When you dial an extension this buzzes or rings that Extension alerting them to pick up...sort of like the old party lines. Newer electronic intercoms such as Mitel provide dial tone and ring back tone but buzzers are still in a seoeratevpair to each Phone or for that matter mounted on the phone jack with a conventional unmodified phone plugged into the jack.

Picture of Mitel 19 Station electronic box bottom right. Above it is part of two 1A2 panels. 1A2 has replacement line cards where as 1A1 is all relay.

This equipment isn't hard to find. I just sold a Shoe Box System which collectors like because if the small size though it doesn't come with an intercom. Remember, these intercoms don't need the 1A1/2 systems to work.



Quote from: rdelius on February 19, 2018, 12:34:26 PM
A dial selective intercomdoes not have a dial tone or ringback

Thanks for answering that question. The lack of those two features certainly do make the prospect of using a key system less attractive (for me, anyway).

Quote from: compubit on February 19, 2018, 08:35:39 PM
The 1A-series intercoms where you can "dial" a phone, basically have a separate box, which listens for either the tones or counts the pulses, then triggers one line, which you feed with either 90VAC to the bell or 10/18 VAC to a buzzer...

Thanks, Jim. That explanation does make sense and is very helpful. And if you took the time to sketch out that schematic just to help answer my question, I'm most impressed and thankful.

Quote from: AE_Collector on February 19, 2018, 11:14:03 PM
In other words, the talk patch is there for all switching. When you dial an extension this buzzes or rings that Extension alertingbthem to pick up...sortbof like the old party lines.

Thanks, Terry. Between your explanation and Jim's above, I can see just why you earlier said that a 1A system isn't really what I want. Perhaps I might tinker with one in the future when I have more space, but for now at least, I'm pretty confident that a Panasonic PBX will be a fast, easy, cheap, and space-efficient way to get started. Then if I want to get more ambitious later, I might try constructing that ten-line miniature exchange that Owain posted the schematics for—which in some ways seems to be precisely what I want (just a challenge to build). And if I find myself with lots of available room in the future, lots of time to devote to learning how to get and keep it working, and can find one, I might try to get an old step-by-step switch.


Hi everyone-

Just a quick follow-up: I did purchase a Panasonic Easa-Phone 616 PBX and two Western Electric 500 telephones—later models with all modular connections.

As expected, it does just about everything I expected it to. Getting it running couldn't have been simpler, and for the price (about $30), I couldn't imagine a more complete solution.

If I had to list any disappointments, it would be these few:

The various system tones are kind of alien to someone accustomed to Bell System sounds. I thought I saw a video of someone demonstrating a Panasonic PBX where its dial tone was basically the same as generic ESS dial tone, but on my unit, the dial tone is a very different sounding tone with a higher pitch. The other sounds are likewise very un-Bell: Ringback, busy, and reorder tones seem to be the same dial tone, just halted with different cadences. I'm not particularly fond of the UK-like double ring cadence either, but at least it's coming from the same physical bell on the receiving end.

The more problematic feature for me from a functional standpoint is how quickly the system jumps from dial tone to a reorder tone—which seems to be about 10 seconds. As I'm trying to teach my two-year-old how to dial, ten seconds will often pass by the time she finds the right digits and dials them, so I frequently have to tell her to hang up and try again. Granted, this is a use case that Panasonic probably wasn't considering. Perhaps this timeout is programmable with an Easa-Phone set; I'll look through the PDF of the manual I have. My daughter is happy just to have her phone's bell finally ringing.

About the phones themselves: One seems to be OK, but the other isn't transmitting voice. I posted a thread on it in the troubleshooting board in case you're interested and would like to help out: