"The phone is a remarkably complex, simple device,
and very rarely ever needs repairs, once you fix them." - Dan/Panther

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Across The Web / Re: Benedetto Buffalino's phon...
Last post by countryman - Today at 03:37:53 PM
I hope in his legislation it is OK to use a phone while driving a vehicle  ;D

The artist has done more pretty funny installations, look at the website
His aquarium booth has been mentioned here on CRPF quite a while ago:
Quote from: MMikeJBenN27 on Yesterday at 12:18:57 AMThey used to offer phones in this color, Oxford Grey.  I think the only way you could get a handset nowadays that color is if it is for one of those phones, and that color is rare.


I disagree. "Dash 52" (oxford gray) handsets with armored cords should be available --- somewhere. Some 234G or 236G multi-slot coin collectors (payphones) with --52 handsets have appeared on eBay. An oxford gray handset with a defective transmitter or receiver could possibly be sawed open on one end and reglued -- not perfect, but possibly acceptable.

I will look around Sonny's warehouse for a slate blue (dash 293) handset. I seem to recall that we purchased some extra slate blue, black, and bright red handsets back in the 1990s. These have the AT&T unused plastics along with used but tested T1 transmitter units and U3 receiver units.

I purchased an oxford gray 500DR-52 sans handset on Ebay a while back. I need an original handset for it. Unfortunately, an oxford gray payphone handset won't look right because of the enlarged hole for the armored cord.
Across The Web / Re: Benedetto Buffalino's phon...
Last post by Kellogg Kitt - Today at 02:24:37 PM
These early mobile phones were the best thing we had before the invention of cell phones.

Quote from: G-Man on Today at 01:19:56 PMIf I had realized that your payphone is already a "frankenphone" and you are not concerned about being period correct, only with its cosmetics (which is fine), then I would not have wasted yours and everyone else's time and bandwidth with my useless trivia.

I didn't consider it a waste of time at all. I thought it was a very interesting post. Even if I don't have any application for all of the information in your post right now, I may at some point in the future, not to mention other people looking to restore or refurbish their payphone who may be able to use the information.

So with an L-type receiver, I'd also need an adapter to use it in a G-type handset shell, and a zinc weight as well, neither of which I'm likely to find anywhere. Do you know what they used for receiver elements before the L-type, for example, in an early single-slot or even a 3-slot payphone with a G1 handset? Was it just a regular U1?
I didn't mention a specific receiver, only an "L-type" because IIRC, AT&T eventually replaced the "LB1" with the progressively newer "L-type" receivers as they were being developed. The specific reference to an "LB1" is in the quoted BSP/Western Electric documents.

ISTR that the reason they initially migrated to the "L-types" for payphone handsets was because they were small enough to accommodate the external coil required for the then new ADA requirements.

It also helped that they were very efficient and were already manufacturing "boatloads" for Trimlines and other applications. Eventually they started using them (with an appropriate adapter) in 2500-sets and other instruments.

Yeah, the weight really was needed when used in a public environment. In a location such as in a home or other sedate setting, it should be ok since the user is generally more diligent in replacing the handset. but the stainless steel armored cord can cause problems (particularly if twisted) with properly seating the handset in the cradle and fully activating the hookswitch.

If I had realized that your payphone is already a "frankenphone" and you are not concerned about being period correct, only with its cosmetics (which is fine), then I would not have wasted yours and everyone else's time and bandwidth with my useless trivia.
Quote from: G-Man on Today at 07:35:42 AMUntil you determine the date and model and manufacturer (WECo or AT&T) of your single-slot payphone, you won't be able to determine the appropriate handset for it. You should not have a problem in doing so since it will be well marked.

I'm not aiming to have the exact type of handset that my payphone would have come with new. I don't see any feasible way of accomplishing that anyway, short of finding a complete original handset/cord assembly, which I don't want because of the cemented-on receiver and transmitter caps (and I wouldn't want to destructively disassemble an original to obtain its parts unless its shell was already broken or cracked).

My payphone isn't otherwise all original anyway. It has a Protel 8000 chassis (which it already had when I got it), and the keypad/hookswitch assembly that it came with had a large crack in its plastic mounting frame, so the whole keypad moved in and out as you pressed buttons to dial a phone number. I replaced it with an NOS one I found, but it was an older type with screw terminals for handset wires with spades instead of a 4-position connector (which is good, because screw terminals make the best / most reliable electrical connections). On top of that, the face plate, cradle hook, and coin-return lever all had a lot of corrosion bubbling through the chrome (and the face plate was dented too), so I replaced those with new aftermarket ones.

For the handset, I just want one with a real WE or AT&T G-series shell in a color that could have come on a single-slot payphone (regardless of its exact model number and date of manufacture). The black AT&T G15A I'm using right now is fine. I'd rather have a gray one, but I don't think that will happen.

I'd also like to have WE or AT&T payphone-specific transmitter and receiver elements. I already ordered a T2 transmitter, but I don't know about the receiver. You mentioned "LB1," but I can't find any information about it, except for this:

QuoteThe dumbbell shape of the 1905 receiver was dictated by the long bar magnet required to produce an adequate signal. Technological advances have resulted in the LB1 receiver for the TRIMLINE hand-set. This unit is only 1/18 as heavy and 1/8 as high as the 1905 model.

So it's the same receiver that was used in Trimlines?

I don't see why they needed a zinc weight with the LB1 receiver. A normal U1 or U3 receiver element only weighs 2.7 ounces, and even if you had no receiver element installed at all, the handset would still be heavy enough to depress the hookswitch and stay in the cradle, especially considering the weight that the armored cord adds. For example, my current payphone handset, with G15A shell, T1 and U1 elements, lanyard wedge, anti-rotation block, and 54" armored cord with lanyard weighs about 12.5 ounces if I hold the far end of the cord in the air while the handset is on the scales. If I removed the U1 element it would weigh 9.8 ounces, which is still more than a regular G15A weighs (they weigh about 9 ounces), and a regular G15A has no problem staying on the hook.

For the record, the base of my payphone is marked:


The removable upper portion is marked:

W 03 93
Initially the original Ringer Equivalency Number was based on the load presented by a Western Electric type C4 ringer. Later on as other standards organizations became involved, a new method was arrived at to compute it.

When attempting to compute the REN of magneto telephone ringers, other factors come into play including whether they have low or high impedance coils and if condensers (and their value) are present in the circuit.

Also keep in mind that an FXO port does not switch calls, that is the function of the central office or PBX that it normally would interface with.

Below is a description by Western Electric regarding the capabilities of magneto party-lines.
Note that the number of telephones that a magneto instrument can ring is dependent on whether it is equipped with a two, three, or five-bar magneto.


Definitions of Terms

     The following definitions refer to terms used on the following pages in connection with our magneto telephones.

     The number of telephones that can be connected on the same line varies, ranging from 1 to 40 or more. However, a line having more than 20 or 30 telephones connected is usually very unsatisfactory from a service standpoint, except in case of necessity or for temporary service. The reason for this being that a line carrying so many instruments is bound to be in use almost continuously, the bells ringing at very frequent intervals and the user almost sure to be "rung in the ear" or otherwise interrupted during the conversation.

     The following definitions of what may be considered a lightly loaded, medium or heavily loaded line are submitted with the thought that its limits are conservative enough so that under all but extreme conditions the figures given can be relied upon. On the following pages will be found a complete catalog of telephones and opposite the listing of each type is specified the kind of loaded line upon which the particular telephone will give best service. Telephones should never be used on lines loaded heavier than indicated as the maximum for each type.

     The telephone lines referred to are assumed to be well insulated and free from high resistance joints.

Light Loaded Lines A light loaded line is one of less than 15 miles in length and not equipped with more than 12 telephones.
Medium Loaded Lines A medium loaded line is one between 10 and 30 miles long and equipped with from 10 to 30 telephones.
Heavily Loaded Lines A heavy loaded line is one up to 40 or 50 miles long or equipped with up to 40 telephones. Lines loaded with this number of telephones are rapidly going out of use and being broken up into shorter lines with fewer number of telephones. Lines of this length or loaded with this great number of telephones should be discouraged in all cases except as before stated, in cases of extreme necessity or for temporary service.
Long post, (Basically is my diagram correct or nonsense)

Thanks. So 1 REN is 20ma so 5 is 100ma. What these magnetos can put out is another question. A party line with 10 ringers is 200mA. 50 is 1A, that is assuming the bells were all 1 REN. So would assume they were pretty beefy.

Evaluating the LDA110 setup:

Effect of the 1K resistor on talk? It's bypassed by the double diode, right? they are 0 ohms. Or say like 3, so parallel diodes with the 1000 ohm resistor is ~3 ohms. That is they present 3 ohms to the circuit. This is a guess, can't work it out from the datasheet.

So in a ring situation, we have the load of the ringers 20-100mA and 2333-7000 ohms. This additional 3 ohms is added and can be thought of as R1 of a voltage divider, R2 the ringers. So, (RMS)

REN 5 (100mA):
100v x 2333 ohm = 233300
                  ----------- = 99.87V across r2 so 0.13v across R1.
3ohm + 2333 ohm = 2336 ohm

REN 1 (20maA):
100v x 7000 ohm = 700000
                  ----------- = 99.96V across r2 so 0.04v across R1.
3ohm + 7000 ohm = 7003 ohm

REN 50: (big party line, 1000mA + HV)
200v x 140 ohm = 28000
                ----------- = 191.78V across r2 so 8.22v across R1.
3ohm + 143 ohm = 146 ohm

As such this seems like a very volt tolerant method. However, nearly all the current goes through the diodes. Is there another way? I've tried changing the resistance of the diodes with a series resistor, and recalculating everything, but I can't make it work. So, voltage divider:

        Vs * R2
Vout = ---------
      (R1 + R2)

At talk:
        6 * 2000      12000
Vout = ------------- = ----- = 1.5v
      (6000 + 2000)  8000

I = V/r = 6/8000 = 0.75mA thru the circuit.

now, ring voltage (200V RMS):

        200 * 2000    400000
Vout = ------------- = ------ = 50v (but clamped to 10V by the zener)
      (6000 + 2000)    8000

I = V/r = 200/8000 = 25mA total
I = V/r = 10/2000  = 5mA So does that mean 20mA goes thru the zeners? Confused

Now in talk @ 6V, we have 1.5V at 0.75mA at the LEDs.
At ring @ 200v we have 10V clamped at the LEDs, and 25mA?
At ring @ 100v we have 10V clamped at the LEDs, and 12.5mA?

Either way at talk voltages, we can trigger an LED, and use very little mA. And at ring voltages, even high ones, the mA consumed is about 1 REN. Have I got this circuit correct? is this what you had in mind ka1axy?

It is designed to detect pulses but as seen also detects rings. And, so we need to still detect rings separately to mask them. However since only this device can initiate a ring on the FXO side, we will know this anyway.

I did a quick search for the LDA110 and it looks like its out of stock, The Vishay H11AA1 was recommended in a forum, but the datasheet seems to be missing the min voltage. Can anyone recommend optocouples?


I've been looking at dial tone generation, and DTMF. how does the WE 1500 & 2500 generate tones? Datasheet:

leejor, I think you are misunderstanding. The FXO port has to dial the device. It can use tone or pulse, but the intention is to signal TO the device, FROM the FXO. This then selects a ring tone. The magneto phones can't dial :)  When you wind a magneto, this device detects it, and sends a ring to the FXO port, which is then forwarded to an operator.
I like how the try to sell the functionality of the unit, clearly in order of practicality; "Good for play and gossip... makes a fine intercom too"  ;D