new member requests help

[G-Man]

Corrected Text-

Because different manufacturers produced magneto sets with a myriad of circuit designs that were not intended to be used with a common battery, your system could be experiencing a current loop caused by such things as perhaps the battery is wired to the sets BATT. TERM. in reverse, or the L1 and L2 wires are transposed.  Another reason could be that the switchook contacts are inserted in a different part of the circuit on the other telephones and the voltage is being looped through the other circuit elements  because of these transpositions.

Also, please be advised that a battery retard coil (a.k.a. choke/repeating/impedance coils) does not isolate dc voltages. If it did dc voltage would not appear at its output. Instead it is intended to reduce the current to the transmitter which would otherwise "fry."

A true Hayes Common Battery System will isolate the A.C. voice currents but not D.C. from the various circuits that are connected to it. 

Once you determine that ...

1.   The set is wired correctly
2.   The hookswitch contacts are opened when the receiver is on-hook
3.   The 1uf condenser is not shorted

You should disconnect the "common battery" and in its place connect an separate battery as was intended by the manufacture in the first place.

On another note, while sometimes used, 6-volts is a little on the high side.

Typically 3-volts (two dry cells) were specified for the transmitter circuit in order to not damage it over the long term. In some cases, on long-loops, 4.5-volts (three dry cells) were also specified.

[G-Man]

Assuming that the NECo N1417CG is wired correctly and that the contacts and condenser are ok, then the problem most likely lies with the "common battery" scheme.

If the wires to the battery terminals are transposed in relation to the how they are connected to the other sets, then the resulting reversed polarity is back feeding  into the internal retard coil (a.k.a. choke, impedance coil), and completing the circuit through the induction coil/receiver to L-1.

If an isolated battery was used as intended then polarity would not be an issue.

You can always reverse the affected wiring however two Eveready or Duracell alkaline batteries would most likely last over a year in the light-duty service these instruments are likely to see.

[Sligichan]

G-Man & Unbeldi,

Thanks so much for increasing my knowledge of what problems might be in my system. Since "common battery" is a very specific term in telephony, I appreciate the suggestion of using the term "shared battery" which is what my set up really is. 

I was inspired to incorporate a shared battery as I had extra wire pairs already in place, seemed an easy solution for my 5-8 phone system, and I could use one, rechargable, 6v battery at a 66-block to provide current on a separate wire pair to each phone's BATT input connections. I had first seen this at this site <http://valhallatreefarm.com/magneto%20phone/phonemagneto.htm> where they have phones in several buildings but use four shared batteries to  power 12 phones.  Of course all phones were same manufacturer, Leich, which probably reduces potential problems.

I did experiment with putting two D-cells on the NE 1417 and there was no scratching sound in the receiver on-hook when batteries connected.  I then put back on the shared battery source but reversed the polarity and BINGO, no scratching sound in receiver on-hook as there was before.  Mixed polarity is clearly an issue with shared battery source but this changed connection would hopefully solve the current drain from the shared battery. However,having now reversed the polarity of the BATT connection,  voice circuit works and no voltage across LINE 1 &2 when receiver on-hook but now magneto ringing won't function. Solved one problem and seemed to create another. I would still like to make the shared battery work for this system and will have to ascertain that polarity is the same at each battery connection for  each phone.  Thanks for pointing out that 6v may be excessive for the purpose and I can reduce that.

Is there such a thing as an isolated battery source for multiple phones that incorporates a shared battery?  Does the system at Valhalla Tree Farm cited above work with shared battery only due to all the phones being same manufacturer?

Very much appreciate your discussion of the issues.

[G-Man]

The Leich 901 belongs to a group of unique instruments that were designed to convertible to either local or common battery service.

Presumably his instruments are still configured for local battery service but he using them in a mixed local-common battery mode.

He is using multiple batteries throughout his system along with what he calls a relay isolator.

Please note that he is using the same model of instruments throughout.

The use of car batteries is overkill, especially when you take into account that these instruments provided service on multi-party lines, some in excess of 20-miles, with only 3-4 volts for talking battery.

Perhaps someone will have the time to take a look at the schematics of the various instruments you are using to figure out how to interface them on your system.

Or <sound of broken record playing> you could always go to Radio Shack or another parts dealer and get battery holders for two "D" cells and connect them at each location.

Another avenue may include doing as tree-farm guy apparently has done, is to keep experimenting with various connections until it somehow works.

After all, if it works why knock it?

[G-Man]

Here is an example of the type of battery holder that I referenced:

•  http://www.allelectronics.com/make-a-store/item/BH-142/BATTERY-HOLDER-2-D-CELLS/1.html

[G-Man]

The beauty of magneto systems was in their simplicity and ability to connect large numbers of instruments separated many miles apart without the need for neither great expertise nor expense.

They were so robust they were able to operate on wires that were in such poor condition that common battery manual and dial service were unable to use them.

The use of barbed fencing wire was frequently used but voice and ringing signals could be sent over long distances.

At the turn of the last century, they helped our agrarian communities to gain their voices for the first time, improve efficiencies and gain access to broader markets for their crops and products.

Even though they are not used as frequently as they once were, magneto instruments which are compatible with those manufactured over a century ago are still being utilized by our armed forces.

This is not a critical criticism since most of us enjoy trying to "improve" on things by experimenting and tinkering with hardware and established practices but after 40-plus years in the telephone industry I tend not to hack equipment unless there is a clear reason to do so.


If this instance a solution is being asked for what is essentially a non-existent problem. I suspect that the battery and charger exceed the cost of individual batteries and their holders.

Also, as part of the simplicity mentioned above, only two-wires (in some cases only one-wire with a ground return) are required instead of the costly multiple pair cable that you installed to each telephone.

Modern alkaline cells have several years of shelf life and will most likely last over a year in telephone service.

Again, this is not a critical criticism but rather a short missive to give some insight as to why I am a proponent of connecting this equipment in the manner its originators intended.

That said, you equally seem to be intent upon using a battery that is common to all of your instruments and I am confident that either someone else will be able to help you accomplish it or you will be able to figure it out on your own.

Good luck in your quest.

[Sligichan]

G-Man,

Thanks very much for your advice...well stated.  Yes, the cost of rechargeable batteries and chargers has exceeded the cost of just some D-cells and, yes, it now appears to be a solution to what should not have been a problem in the first place.  Perhaps seduced by having all those extra pairs of wires right there begging to be used.  I actually thought it was quite an elegant solution...such hubris!  I do have a penchant for making projects more complicated than they need to be...just ask my wife.

Maybe I will keep tinkering, and it is fun, and thanks to folks such as yourself I have learned quite a bit.  Thanks again for your patience and knowledge.

[G-Man]

Please don't ever let anyone to dissuade you from "tinkering" or experimenting! It's both fun and educational, and helps us to expand our horizons.

And by all means, if you still wish to do so, continue to search for a solution to your shared battery problem.

G-Man,

Thanks very much for your advice...well stated.  Yes, the cost of rechargeable batteries and chargers has exceeded the cost of just some D-cells and, yes, it now appears to be a solution to what should not have been a problem in the first place.  Perhaps seduced by having all those extra pairs of wires right there begging to be used.  I actually thought it was quite an elegant solution...such hubris!  I do have a penchant for making projects more complicated than they need to be...just ask my wife.

Maybe I will keep tinkering, and it is fun, and thanks to folks such as yourself I have learned quite a bit.  Thanks again for your patience and knowledge.