AE Railroad Telephones

[Brinybay]

Splitting this off my find of OPS that was in the Flea Market/Yard Sale board. 

I joined the ranks of RR phone owners.  I found a Type 60 AE the other day in a box of other phones at an antique store.  I had no idea what exactly it was at first.  Thanks to Google, it didn't take long to find it in a GTE/AE catalog from October 1975, pg 17.  I'm happy to know that it wasn't "frankened" with modern parts.  The manufacture date (Feb 20, 1969) confused me at first because except for the handset, it's overall appearance resembles phones from the 30s era.  I think it's missing the cover for the back of the magneto though.  I'm interested in knowing how these things were used, such as were they dedicated for RR communication line only, or did they function for outside lines as well?  Any RR enthusiasts out there?  I'm not particularly a RR buff, just old phones of almost any sort.  It would be interesting to see what other phones collectors have that were dedicated for RR use. 

[unbeldi]

The induction coil in your box looks, if not identical, at least very similar to the induction coil in an Automatic Electric RR subset that I have, which was used to connect a scissor-type transmitter arm, or a desk stand, to RR lines.

Here is a view of the induction coil, seen just behind the condenser in the front.  It is mounted in one of those small Type 32 Bakelite extension boxes and has a push-to-talk button.  The boxes already showed up the AE catalogs in the 1930s, for various applications, including as relay boxes, small ringers, and local extensions.

I have not found much RR equipment documentation for AE stuff either, and I am always looking.  Railroad telephone technology changed very slowly, and what would be considered archaic systems still existed in abundance in many places.  A friend told me that in some old subway station in NYC scissor-type transmitter arms could be observed in some old control booths even in the 1990s, albeit probably unused by then.   I have a WECo 1348D  RR transmitter arm for local battery service that was still refurbished with new parts (bull-dog transmitter) in 1955. Same situation in Europe. I have a 1962 Yugoslavian (! Tito era) magneto phone in mint condition, never used apparently, which was a copy of a 1933 German local battery telephone, the OB33.  Even in Germany, those were still to be observed in the field until the 1990s, I was told or read somewhere.

There is some good documentation, in the TCI library and elsewhere, about the Western Electric RR systems.  The technology didn't change much over the years.  A 501A subset pretty much was the same in 1949 as it was in 1924, albeit having been renamed as 501E, IIRC.  I think they changed the paint. :-)

[unbeldi]

Was the induction coil in your set completely cut or disconnected from the rest of the wiring?

[unbeldi]

I found a better picture of my induction coil with the number stamp on it.
Does yours have any identification?

[Brinybay]

Was the induction coil in your set completely cut or disconnected from the rest of the wiring?

No, it's still attached.

I found a better picture of my induction coil with the number stamp on it.
Does yours have any identification?

Yes, see pic. 

[unbeldi]

Oh, now I see the geometry of the box.  The coil is on the wall side of the base plate and the wires disappear through the hole.


The ringer is a straight-line ringer and the has right size condenser for that, 0.7 µF.
So, they isolated the high-voltage carrying parts to be under the base plate toward the wall.  So, I suspect the condenser there is in front of the coil in the incoming line.  Is it a  0.25 or 0.5 µF  unit?

Hmm, but this has a hand generator, so it was not installed directly on the line.  I think this is a siding station set, and the generator is to call the main office at the station over a local line.

[Brinybay]

Oh, now I see the geometry of the box.  The coil is on the wall side of the base plate and the wires disappear through the hole.

The ringer is a straight-line ringer and the has right size condenser for that, 0.7 µF.
So, they isolated the high-voltage carrying parts to be under the base plate toward the wall.  So, I suspect the condenser there is in front of the coil in the incoming line.  Is it a  0.25 or 0.5 µF  unit?

Hmm, but this has a hand generator, so it was not installed directly on the line.  I think this is a siding station set, and the generator is to call the main office at the station over a local line.

Correct about the siding station, it says in the catalog page that these were to be installed in siding booths.

You must be referring to this part on the back?

[unbeldi]

Yes, that's a 0.5 µF capacitor.   It is too small to block DC from a receiver as in the typical induction coil telephone, and AE usually used enormously large caps for that, anyways.   So, how is it used?   It is also tested to 1000 V break down voltage, so it must be sitting in front of the coil on the line.  I have an idea for a circuit of this box since I know the construction of my coil.

Will you be tracing the wiring of this phone?
Does the handset have a push button in the handle?

[unbeldi]

stub posted a similar phone, labeled as L-653   here

By the diagram, that has a standard induction coil and also a 0.5 µF capacitor.   However, the ringing cap is 2 µF !

Nope, strike that about the induction coil, that coil is a rail road coil too, I am judging it by the high DC resistance ratio from primary to line-side.

[unbeldi]

Ok, here is a circuit diagram.

All I had to do is expand the diagram of my subset with the ringer and the generator and add/rearrange the switches.
The result is the circuit of AE FORM D-53983 as displayed in Stub's phone.

The difference to your phone we have to work out, but I expect them to be minimal.  We know that the ringing capacitor is 0.7 µF, not 2. I suspect that stub's phone used low impedance ringer.

In your handset should be push-to-talk switch which enables the transmitter and introduces a resistor into the receiver path, so that audio can still be received.  This is a common feature on way station sets.  Often I have seen the resistor to be 1500 ohms, here it is 700 Ω.

From the diagram we see that the telephone itself, i.e. the audio circuitry for the transmitter and the receiver, is completely isolated from the line.  The line connects across a high-impedance winding, protected with the 0.5 µF capacitor, which protects up to 1000 V.

The hook switch, the HS switches in the diagram,  switches the line from the ringer to the induction coil and also turns on the local battery current to the transmitter.  Thus the transmitter is powered and connected to the low-impedance (2 ohms) primary winding of the induction coil, when the push-to-talk button on the handset is also pressed.  The signal is transformed outward to the line side secondary of 150 ohms DC resistance.  This winding likely has an extremely high impedance at voice frequencies, my guess is 10,000 ohms or more.

The receiver is driven from the line to an 11 ohm (DC) winding.

The ringing bridge is typical, nothing special to mention, except that it is disconnected when the phone is off-hook, and the generator is simply switched onto the line when operated by its built-in switch, which normally shunts the generator.

From all this we see that the principles of this phone are quite different than our garden-variety home telephones.

Hope this helps.

[Brinybay]

Will you be tracing the wiring of this phone?

No, I don't do tracing.  I take macro pics of wiring and refer to those if I need to.  Lacking that, I use the "by guess and by golly" method of trouble-shooting.

Does the handset have a push button in the handle?

Yes.

[Brinybay]

Ok, here is a circuit diagram.

All I had to do is expand the diagram of my subset with the ringer and the generator and add/rearrange the switches.
The result is the circuit of AE FORM D-53983 as displayed in Stub's phone.

The difference to your phone we have to work out, but I expect them to be minimal.  We know that the ringing capacitor is 0.7 µF, not 2. I suspect that stub's phone used low impedance ringer.

In your handset should be push-to-talk switch which enables the transmitter and introduces a resistor into the receiver path, so that audio can still be received.  This is a common feature on way station sets.  Often I have seen the resistor to be 1500 ohms, here it is 700 Ω.

From the diagram we see that the telephone itself, i.e. the audio circuitry for the transmitter and the receiver, is completely isolated from the line.  The line connects across a high-impedance winding, protected with the 0.5 µF capacitor, which protects up to 1000 V.

The hook switch, the HS switches in the diagram,  switches the line from the ringer to the induction coil and also turns on the local battery current to the transmitter.  Thus the transmitter is powered and connected to the low-impedance (2 ohms) primary winding of the induction coil, when the push-to-talk button on the handset is also pressed.  The signal is transformed outward to the line side secondary of 150 ohms DC resistance.  This winding likely has an extremely high impedance at voice frequencies, my guess is 10,000 ohms or more.

The receiver is driven from the line to an 11 ohm (DC) winding.

The ringing bridge is typical, nothing special to mention, except that it is disconnected when the phone is off-hook, and the generator is simply switched onto the line when operated by its built-in switch, which normally shunts the generator.

From all this we see that the principles of this phone are quite different than our garden-variety home telephones.

Hope this helps.

Thanks for the diagram and the detailed analysis.  I'm sorry that I'm not able to converse with you about the electronic details, I'm not educated in electronics.  My wife and I have been considering getting a shed for me to use as a work shop, and it would be fun to have a couple of magneto phones set up between the house and the shed so we could "ring" each other when needed, but I would only need very simple instructions and how to do that, e.g. which wire goes where and what kind of magneto phones would be compatible.  I'm not even sure this one works, so some simple instructions on how to test it would be nice.

[unbeldi]

Hi again.

I think setting up a private magneto line is a great project, and sure to be fun.

While I haven't taken measurements on your phone or induction coil, clearly, to be certain, however I do think that to make this phone work with another phone, you're going to have to get another one like it, or another railway phone that uses similar technology.  It could be another AE model or a WECo model, I think they would be compatible.  AE explicitly made RR equipment compatible with WECo systems.  That little subset I showed, in fact, was intended to be used with a WECo transmitter arm (1148D).

Yours is not a normal magneto phone and won't work properly with those for non-railroad use. The audio reception will be extremely weak both ways, unusable.  The induction coil has a very high impedance of several thousand ohms, while a standard "home" telephone set only has an impedance of several hundred.  So when hooked up together there is a gross mismatch with a very poor transmission efficiency.  For best efficiency the impedance at the source and destination should be about equal. For standard phones this is typically between 600 ohms and 900 ohms.

[Jack Ryan]

The Type 60 telephones are interesting and were made over an extended period. The earliest I have seen looked like an AE 3 with a magneto but I am not sure it was called a Type 60 at that time. The type like Brinybay's were updated slowly with newer and newer components like bell, handset and IC.

There are some with dials and at least some of those use simplex dialling and some with hook latches. Clearly many were used on party line circuits. The PPT button (which also changed over time) was less to conserve battery power and more to cut down on local noise feeding into the transmitter and interfering with the received speech.

I have attached some pictures of:
1. A later PTT button
2. The rear of an AE 65 - there is no additional cover
3. An example circuit.

Sorry, I couldn't find a picture of a hook latch. I have such a phone but it is stored and not easy to access for the time being.

Jack

[unbeldi]

The Type 60 telephones are interesting and were made over an extended period. The earliest I have seen looked like an AE 3 with a magneto but I am not sure it was called a Type 60 at that time. The type like Brinybay's were updated slowly with newer and newer components like bell, handset and IC.

There are some with dials and at least some of those use simplex dialling and some with hook latches. Clearly many were used on party line circuits. The PPT button (which also changed over time) was less to conserve battery power and more to cut down on local noise feeding into the transmitter and interfering with the received speech.

I have attached some pictures of:
1. A later PTT button
2. The rear of an AE 65 - there is no additional cover
3. An example circuit.

Sorry, I couldn't find a picture of a hook latch. I have such a phone but it is stored and not easy to access for the time being.

Jack

Jack, I think you are confusing this phone with others, similar ones that were for standard telephone service.
The pushbutton in the siding station phone had a slightly different function in this phone.  It is not a transmitter cut-out button, but a push-to-talk switch which closes the transmitter circuit when pushed, in conjunction with the hookswitch, and inserts a resistor into the receiver circuit.  This is not to lower noise, but to enable the user to be able to hear the dispatcher even while talking but at reduced volume. The dispatcher sat in an booth office and didn't produce much noise. Noise would come from siding stations, therefore the handset has the transmitter normally cut off when off-hook, until the button was pushed.

The civilian versions of the phone had a completely different circuit, much like the AE40, an AST circuit.


PS: Thanks for posting the diagram.  If you compare it you will find that it is the same circuit as the one I drew earlier in the thread.  Better yet, it probably is the correct diagram also for Brinybay's phone, because it contains the same 0.7 µF capacitor for the ringing bridge.  I think the difference is simply that both phones use a high impedance ringer, w/r/t the 2 µF capacitor in older sets with low-impedance ringers.

The DC resistances of the induction coil windings printed on your diagram are exactly the same as on my AE RR subset. 144 Ω / 3.3 Ω / 14 Ω are the values, so this is the exact same coil and replaced the older coil I drew in the diagram.