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Homemade Telephone Network


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#1 shadowman3478

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Posted 16 May 2009 - 07:19 AM

Hi, this is my second post.

I'm building a little two way phone network thing that i plan on expanding eventually. right now i simply have set up two phones powered by a 9v battery and a 330 ohm resistor.

i'm just wondering what a easy way i can make the other end ring is. i've read that you need a 90v battery but i'm not sure where i would wire it. would i just replace the 9v with the 90v? (or whatever volt battery i would need).

i appreciate your replies.

#2 rbcp

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Posted 16 May 2009 - 11:29 AM

You should get a 3-position switch and wire 9 volts to one, 90 volts to the second, and then nothing to the third.

So 9 volts actually works? I thought off-hook voltage was more like 24 volts.

#3 jfalcon

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Posted 16 May 2009 - 11:32 PM

It needs to be 90v *AC* at 20hz to ring the bells.

http://www.sandman.c...ingvoltbul.html

#4 shadowman3478

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Posted 17 May 2009 - 02:42 AM

hey thanks guys! all of that information is think is going to help me!
i'd be happy for any other information on the subject as well. this is turning into something of a hobby for me and any links that might help or useful tips/tricks/etc will be much appreciated! :P


:edit: would i find the 3 position switch at radioshack? and yes rbcp, it does work at 9v just as an intercom system. but it seems to only work with the simple cheapy phones you can get at att or wherever for 5 dollars that only run on AC and with no ring.

Edited by shadowman3478, 17 May 2009 - 02:54 AM.


#5 ThoughtPhreaker

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Posted 17 May 2009 - 11:19 AM

This probably wouldn't work on a day to day basis, but if you're looking for a quick and easy solution, one thing I found works quite nicely is you can generate a loop of 20 hz on your computer, take the output of your sound card to a preamp usually used for turntables, and send the output of that directly into the phone. Adjust the tone/gain settings for best results.

EDIT: Also, it doesn't have to be *exactly* 90 volts. Most phones will run just fine on a lower amount of current. Some electronic ringers just listen for the 20 hz, not the voltage. I'm willing to bet if you play 20 hz into an audio interface on one phone while, say, your average cordless phone on the same line is hung up, it'll start ringing.

Edited by ThoughtPhreaker, 17 May 2009 - 11:24 AM.


#6 shadowman3478

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Posted 18 May 2009 - 06:11 AM

You should get a 3-position switch and wire 9 volts to one, 90 volts to the second, and then nothing to the third.

So 9 volts actually works? I thought off-hook voltage was more like 24 volts.


hey rbcp, where can i get one of these 3 position switches? do you have a link by any chance?

#7 dinscurge

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Posted 18 May 2009 - 08:09 PM

You should get a 3-position switch and wire 9 volts to one, 90 volts to the second, and then nothing to the third.

So 9 volts actually works? I thought off-hook voltage was more like 24 volts.


hey rbcp, where can i get one of these 3 position switches? do you have a link by any chance?

you can get them at radioshack, its just a spdt, or dpdt if you want just make sure to get a decant one, depending on the 90volt battery it may have more current than a submini/mini can handle. what did you do anyways to get it to work? just hook up a phone line to each phone and and attach power? also yes phones dont need 90volts remember from an old kipkay video being like 67 volts for his phone line, probably depends on how far away you are from the transformer.

Edited by dinscurge, 18 May 2009 - 08:10 PM.


#8 Mr. zip

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Posted 19 May 2009 - 01:15 AM

For a basic 2 phone loop, 9volts is fine. IIRC, -48volts is the standard, but that also has its roots in the old systems. As someone above stated, ~90volts AC at 20hz is needed for ring. While you can spoof newer electronic ringers with sending a simple 20hz DC biased signal, it would never work with actual bell ringers.

I dont know how hard they are to find, but you could always find the magneto out of an old magneto set, they will even ring modern phones. (You get spoiled having a grandfather who worked for bell. I have all sorts of old phones to play with).

#9 dinscurge

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Posted 19 May 2009 - 01:22 AM

if you cant get it to ring you can use an oscillator, or a buzzer. that will run of 9 volts.

#10 shadowman3478

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Posted 19 May 2009 - 08:30 AM

what did you do anyways to get it to work? just hook up a phone line to each phone and and attach power?


yeah i just took a normal phone line and cut the red wire inside and attached it to a 9v battery and a 330 ohm resistor which i read regulates current or something like that.

Edited by shadowman3478, 19 May 2009 - 08:31 AM.


#11 Skunkworks

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Posted 23 May 2009 - 10:34 PM

You don't need that resistor actually. You can just as easily run the phones off any DC adaptar that plugs into the wall with a voltage of 6 to 12 volts.

One possible way to ring non electronic phones is to use a 4:3 stepdown transformer from mains, this will obviously put out 60hz, but it should work for old style phones.

For a real 90v 20hz inverter, look on google. Its not at all hard to find the right schematic.

#12 dinscurge

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Posted 01 June 2009 - 06:26 PM

going to hijack lols. i found an old 1 to 2 splitter going to post pics eventually probably going to rip off the phone company for the ring voltage as it has 1male to 2female so just plug it into the wall but not sure how to connect everything, as it splits the re,gr,ye,bl lines to be line 1 green and red to be pins 3, and 4 and line 2 to be yellow, and black for pins 3 and 4 also. red is in the same pin as yellow so if pins are starting at 1 on the right red and yellow are on pins 3, and green and black are on pin's 4. so i should connectthe 3rd pin of each red/yellow to 9 volts positive to one negativ to the other, and bridge the black/green. and since the phone company doesnt make u directly pay for the elctricity i can use the 48 volts or whatever its actually running as long as the phone isnt ringing. so to make each phone ring i would hook up the positive and the neutral? to pins 3/4 of that line 1, or 2 with a switch at each phone to ring the other one?

Attached File  IMAGE_013.jpg   147.79KB   3 downloadsi know its blurry lols contrast all f'd up on camera but w.e. its comes in 4 wires splits to 2 for each line. im guesssing i would connect the green and red for the rinnger switches?

Edited by dinscurge, 01 June 2009 - 06:46 PM.


#13 dinscurge

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Posted 02 June 2009 - 11:44 PM

Attached File  IMAGE_014.jpg   261.2KB   3 downloadsi was bored so took 5 mins to make it. havent tested yet but it should be fine if it was color coded correctly. even had a spare d.c. adapter so i can just use a plug in to distortion pedal powersupply. just have to make a ringer but im lazy/dont care what it sounds like so just going to go from a 9v ac powersupply through a 1-10 transformer to be around 90 volts at 60hz should work fine for class b? electronic ringing phones.

#14 Spoof5.2.2

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Posted 14 February 2010 - 03:37 PM

Hi, this is my second post.

I'm building a little two way phone network thing that i plan on expanding eventually. right now i simply have set up two phones powered by a 9v battery and a 330 ohm resistor.

i'm just wondering what a easy way i can make the other end ring is. i've read that you need a 90v battery but i'm not sure where i would wire it. would i just replace the 9v with the 90v? (or whatever volt battery i would need).

i appreciate your replies.



You can also use a generator. Old Army field phones used small crank or lever activated generators that sent AC ring voltage down the line. The cadence would be off (unless you can manage to create the ringing duty cycle perfectly by hand) so things like auto answer-ers and ring directors wouldn't work right.
As others have stated, it doesn't need to be exactly 90v.

#15 systems_glitch

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Posted 14 February 2010 - 09:24 PM

I've got an issue of Electronics Illustrated magazine from the 60's that describes the construction of an in-home telephone network using surplus rotary dial phones. They've got a circuit that uses a small tube plate + filament transformer and some relays that provides ring voltage, allows the ringing of the other phones on the circuit by means of the rotary dial, and switches over to operating voltage when it detects a second off-hook phone. IIRC, it's just resistors, capacitors, a few diodes and the transformer. I'll scan it if I can dig it up.




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