Back To The Future

Ten years ago I designed a prepay controller for 3 slot payphones.  Two pictures of that controller are shown below.  The logic circuitry is in the black box with the instruction label mounted in the center of the large pc board.  The remaining parts are two power supplies, a bank of control relays and switching to make the controller automatic or manual. 

That design had the following criteria:

1-    Cost was not a factor.

2-    The input of the controller would plug into a standard subscriber line.  The output would mimic the operation of a payphone line circa 1950’s, including the timing of all the functions. 

3-    Any phone connected to it could not be modified or rewired.  The phone must work in its ‘as removed from service’ condition.

4-    It had to operate every prepay model made by Western, Northern or Automatic Electric.  Regardless if it was two piece, handset, single coil relay, double coil relay, rotary or Touch Tone.

5-    It would collect or return the initial deposit on hang-up, controlled by a timing circuit. Called party supervision no longer existed and getting involved with SIT and voice cadence recognition for a hobby project was out of the question.

6-    Any phone connected to it had to be able to answer incoming calls.

7-    Size and complexity were not a consideration.

8-    Any number of payphones could be connected to the output.

9-    It was A.C. powered.

 After six months of circuit design, I ended up with a device that was expensive and complex to build. Fortunately at that time I had the facility around me to do the job. Unfortunately that facility and most of my vendors from that time no loner exist.

After a few dozen of those controllers were manufactured.  If you’re lucky enough to own one better hold on to it.  I won’t be building any more of them.

Over the years I’ve been asked if a more basic, simple, and less expensive circuit for payphone control could be designed and built.  What follows is an attempt to fulfill these requirements in the simplest and most technically ‘creative’ way I can think of.

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Getting To Work

  Unlike the first model, I’m not building these for sale or trade.  This design must be simple enough for any collector to build.

 The new design has the following criteria.

1-    It must be as simple as possible to build.

2-    It must be as inexpensive as possible to build. 

3-    It must be as small as possible so it will fit inside the payphone.

4-    It must be powered by tip and ring voltage.  No connection to the AC line.

5-    It must be built with parts that are readily available.

6-    It must make the payphone ‘coin first’.  No dial tone until the initial deposit is made. Like in the ‘good old days’.

7-    It will only return or collect the initial deposit.  One or the other, not both!  Your choice.

8-    To meet the first three criteria a coin must be deposited in order to answer an incoming call.  The coin will be treated like an initial deposit for an outgoing call when the phone is hung up.

9-    It must work with Western, Northern and Automatic Electric payphones as long as they have a single coil coin relay.

10-   If the payphone already has a single coil coin relay the only wiring changes will be the connections to the controller.

11-   Modification of the coin relay is OK, as long as its original appearance isn’t changed. 

12-    The main purpose of this controller is to animate the payphone’s coin mechanism.  Really making the phone into - A PAY PHONE!                

Due to the characteristics of the double coil coin relay used in early model payphones, it’s not possible to power them from the phone line.  You can however replace the old style hopper and double coil relay with a newer style hopper and single coil coin relay.  Western Electric did that in some refurbished 190 and 200 series phones.  Automatic Electric used both types of hoppers and coin relays in their LPB and LPC series payphones.  Both coin relays are shown in the wiring diagrams and both hoppers and coin relays appear in the parts list for those models. 

However, if you own a Gray/Western 50A or 50G, I suggest NOT doing this to it.

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Sometimes Less Is More

It took about a week to design the circuit and interface it to the various manufacturers’ payphones. 

Fig. 1 is a completed controller next to a battery for size comparison.  The operation of the circuit meets all the design criteria.  It’s not nearly as fancy as the original unit but then again it wasn’t meant to be.  Happy New Year!

Fig. 1

Fig. 2 is a circuit diagram of the unit.  If this circuit had any fewer parts it would be invisible.

Fig. 2

Fig. 3 is positive artwork for the pc board.

Fig. 3

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Building The Controller

        A parts list for the unit is given below.  I sourced the parts from Jameco Electronics only because that catalog was on top of the pile.  I have absolutely no affiliation with them.  The page numbers and costs of each part from their latest catalog are also listed.  They charge a service fee of $5.00 for orders under $25.00.  The minimum shipping charge is $5.95

            I designed the circuit using very common parts that are stocked by all the mail order suppliers (before someone asks, and I’m sure they will).  I used three 10 volt zeners in series because they are a common value; a single 30 volt zener is not.

If you have the facility to manufacture pc boards, artwork for the board is shown in Fig. 3; or the circuit can be hand wired on ‘perfboard’. 

                                  Coin Relay Controller Parts List

Fig. 4 shows the location of the parts on the board.

Fig. 4

        Refer to the pictures below.  Look through your junk box and find different color wires that have a spade lug crimped on one end.  I’m sure you have old wiring harnesses from phone equipment that you can salvage these leads from.

 If the controller is going to be used in a Western Electric payphone, four different color wires each 10 inches long with a spade lug on one end are connected to the pc board output terminals 2, 3, Y, and SL

If you are going to use the controller in an Automatic Electric payphone make the Y and SL wires 3 inches long.

You will need another wire with a spade lug 5 inches long for Step 2 of the coin relay modification.

You will also need a jumper 12 inches long with a spade lug on each end.  You can splice together two short wires each with one spade lug.  Use shrink tubing to cover the splice.  Of course if you have spade lugs, wire and a crimping tool you can make the jumper the proper way.  This is the ‘L’ jumper referred to later in the installation section.

          Use these pictures to double check the location and position of the parts on your board.

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The Single Coil Coin Relay

        The second half of this project is modifying the coin relay.  Since we are using the ‘on hook’ 48 volts to trigger the coin relay instead of 130V used in normal service, the mechanical load and the amount of force necessary to move the armature to the energized position must be greatly reduced.

The electrical characteristics such as the 1K series resistor, the coil shorting contacts and the slow release feature were all eliminated, or are done in a different way.

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Modifying The Coin Relay

It would be great to start out with a payphone that has a working coin relay and a complete hopper but this may not be the case.  Many Western, Northern and Automatic Electric 3 slots had these parts removed.  The internal hopper parts are shown in the picture below.

          If you need a coin relay or parts for a hopper go to:

            http://www.payphone.com/shop/catalog/Western_1A_Relay-p-16385.html

          I’ve never done business with them but the prices seem very fair.  They sell parts for single slot payphones.  The coin relay and internal hopper parts for single slot Westerns are identical to the parts for the old 3 slot payphones.

Assuming you have a single coil relay and hopper in your phone I suggest you un-mount them.  It’s easy to do.  Remove the 3 screws accessible from the vault compartment.  It will be much easier to work on and test the finished assembly if it’s sitting on your bench and not in the phone.

You’ll have to make a few simple mechanical changes to the coin relay.  I’ll bet the second one you modify will take you less than 5 minutes.  This one will probably take a little longer.

Pictures of the original coin relay are shown along-side pictures after each step in the modification.  The tools you need are:  A pair of thin long-nose pliers, a small pair of diagonal wire cutters, a soldering iron, solder and a screwdriver.

Step 1 

 The first picture below is the left hand side of the unmodified coin relay.  It shows the 1K resistor and three solder terminals.  One of the soldered connections is the right hand wire ‘tab’ from the coil bobbin.  It’s highlighted.

 Remove the resistor, wire jumpers and clean off the solder from the connections.  Cut the wire ‘tab’ from the relay coil bobbin where it’s soldered to the lowest terminal.

The second picture shows the terminals without the resistor, wire jumpers and solder.  It also points out the wire ‘tab’ from the coil bobbin that was disconnected from the lowest solder terminal.

Step 2

Two jumpers will be connected to the solder terminals.

Note the black wire in the picture below.  Connect a wire 1.5 inches long between these two points.  The top point didn’t have a soldered connection on it originally.  You’ll have to scrape off the oxidation then ‘tin’ the metal so you’ll be able to solder to it.  A close-up of the tinned edge is shown in the second picture.  The other end of this black wire is soldered to the right hand terminal of the coil bobbin.

          Note the yellow wire.  This is the jumper you made that’s 5 inches long with a spade lug on one end.  Solder the bare end as shown in the picture.

Refer to the third picture.  The end with the spade lug goes to the #1 screw on the other side of the relay.

          The two solder terminals closest to the front of the relay are empty and will have nothing connected to them.

Step 3

            Using a thin pair of long-nose pliers, bend the contact as shown in the pictures below.  It’s the last contact toward the back of the relay.  After it’s bent make sure that it doesn’t touch anything in front or in back of it, regardless of the position of the relay armature.

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Return Or Collect

You will have to decide if you want the coins to return or collect.  Personally I like the coins to return.  Coins will always be in the return chute or pull bucket in front of you.  You won’t have to run around looking for change to demonstrate your ‘toy’ to guests.  Coins will also be there to answer incoming calls.

Refer to the picture below.  Assuming you opt for the coins to return, position the coin vane as shown.  The coin vane is the blue plastic ‘flapper’.  Put a drop of glue or Scotch Tape on the edge of the flapper as shown by the arrow.  Scotch Tape is a better choice if you change your mind later and want the coins to go the other way.

          Refer to the picture below if you want the coins to collect. Glue or tape the Coin Vane in this position.

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The Adjustment Screw

The picture below is a side view of the coin relay.  Push the armature of the relay to the energized (back) position.  It should take very little force to move it smoothly all the way back.  Release the armature and it should spring forward. 

Note the adjustment screw with the plastic cap on the end.  If you manually push the armature all the way back to the energized position, the plastic cap should just touch and slightly push the surface of the flat push back spring.  This is an adjustment that can be changed by turning the screw in or out.

 Its function is to apply enough opposing force to overcome any residual magnetism built up by the armature, causing it to stick in the energized position after the on hook voltage is removed from the relay coil.  This probably won’t happen because the original setting of the screw is usually perfect.  If it does, a slight clockwise turn of the screw (a few degrees) will solve the problem.

The original purpose of this adjustment was timing of the slow release function of the armature, caused by the decay of the magnetic flux, after the relay coil had been shorted by internal contacts in the coin relay.

 It’s interesting that although the theory of operation of the modified coin relay is totally different than its original design, the function of these parts is exactly the same, but for a completely different reason.

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  Testing The Coin Relay And The Hopper

        Testing the coin relay/ hopper assembly is simple.  You will need a modular phone cord with spade ends, an ohmmeter, a phone on a working line and the ability to plug the modular cord into that line while the phone is in use.  You will also need a nickel.  See below.

Connect the red and green leads from the modular cord to terminals 2 and 3 of the coin relay. Makes no difference which color goes where.

The two clip leads on terminals 1 and G go to the test leads of the ohmmeter.  Coincidently they also happened to be red and green.  Unfortunately, those were the only color clip leads I had   that weren’t being used for other purposes.

1- Push the armature all the way back and release it.  This will force the thin plastic Coin Trigger to flip up.  The ohmmeter should now show an open circuit.

2- Take the phone off hook. Make sure you’ve got a dial tone.

3- Quickly plug the modular cord connected to the coin relay into that phone line.

4- Drop the nickel into the top of the hopper making sure it hits and pushes the plastic Coin Trigger to the down position.  The ohmmeter should now show a short circuit.

5- Hang up the phone.  The coin relay should snap closed and stay that way.  The nickel should get tossed out of the side of the hopper.  That is if you set the hopper to return coins.  The ohmmeter should still show a short circuit

6- Unplug the modular cord connected to the coin relay from the phone line.  The coin relay should de-energize and the ohmmeter should now show an open circuit.

7- If the hopper was set to collect coins, the nickel dropped straight down and is under the hopper. 

You can repeat this a few times to make sure everything is working properly.  Besides, it’s fun watching the nickel get tossed out of the hopper.

 Now try these tests with a bunch of quarters dropped into the hopper.  Hang up the phone and watch the quarters go flying.  If you set the coins to collect, the quarters will be stacked in a neat pile under the hopper.

Besides being amusing, there’s another reason for doing this.  The factory specification of the single coil coin relay is the capability of holding the weight of 20 quarters on the Trap Lever of the hopper and then being able to dump that weight when the Trap Lever is released.  You won’t be making $5.00 phone calls but it’s interesting to see if your modified coin relay can still meet the original spec. 

You might want to try this test AFTER the phone is completed.  If you do it now, you’ll be chasing quarters all over the room.

            Assuming these tests were successful, the next step is to install the coin relay/ hopper and the completed controller board in your payphone.

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                  Installation In A Western Or Northern Electric 3 Slot

        Refer to the picture below.  You must start with a working Western or Northern Electric payphone.  It should have a subset or some sort of network wired to it, if that particular model phone requires one.

 For further information on wiring a printed circuit network into a payphone go to:

                                    http://antiquetelephonehistory.com/WE200payphones.php

 None of the original coin relay wiring is used.  You can tape and store the wiring or remove it from the phone.

          1- Mount the controller board with double-sided foam tape to the backboard.

2- The Y and SL lugged wires from the board are connected to the Y and SL screw terminals on the transfer contact assembly.

3- One side of the phone line is also going to screw terminal Y.  The other side of the line is going to the coin relay.

4- The jumper on terminal L is new with a spade lug on each end.  It’s 12 inches long.  The other end of this jumper is connected to the coin relay.  This is the jumper you made that was mentioned in the section on attaching the wires to the pc board.

It is possible to hide the controller behind the terminal board at the top of the phone with the T, TR, and L screws, or in back of the hopper.  You might want to install the pc board this way if you don’t want to change the original ‘look’ of the phone.  You will have to mount some of the parts on the pc board at a right angle instead of standing up, so the finished board will be thinner.

Since this phone is an example of a universal installation, I mounted the board in the most convenient and visible place.

The picture below is a close-up of the coin relay screw terminals.  All the remaining wiring will terminate on these screws.  They are:

A- The other side of the phone line is connected to coin relay Terminal G.

B- The other side of the L jumper is connected to coin relay Terminal 1.

C- The controller wire 2 is connected to coin relay Terminal 2.

D- The controller wire 3 is connected to coin relay Terminal 3.

E- The yellow jumper with the lug (from the other side of the relay) is also connected to Terminal 1.

          That makes a total of 5 leads with spade lugs that go to the screw terminals of the coin relay.

Below is a diagram of the controller connected to a Western Electric 3 slot payphone.

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Final Testing The Payphone

One of the most useful tools you can build if you work on Western Electric payphones is a set of jumper wires 2 feet long with spade lugs on both ends.  There are 5 transfer contacts between the top and bottom of the payphone.  Unless you have x-ray vision it’s impossible to know what’s going on inside the phone when it’s locked up.  If you connect each of the transfer contacts between the top and the bottom with a jumper, you can leave the top separate from the bottom while you do your testing.

Hopefully you made the jumper wires and you can work on the phone with the top separated from the bottom.

1-    Plug the phone into the line.

2-    Lift the handset.

3-    Drop a coin down the throat of the hopper.

4-    You should hear a dial tone and the electromagnet in the phone’s top should click closed.

5-    Try the dial and make sure you can break dial tone.

6-    Hang up the phone.

7-    The coin relay will snap closed.

8-    The coin will immediately return or collect. Whatever you set it to do.

9-    Two seconds later the coin relay will disengage.

 In order to answer an incoming call a coin must be deposited after the handset is lifted.  Use a dime or a quarter.  One nickel will just hang in the coin track waiting for the second nickel before they both drop into the hopper and answer the call.  To keep the design of the controller as simple as possible incoming calls had to be handled this way.

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And

Remember that everything mentioned above also applies to Northern Electric payphones - including those very well built 10 and 12 button Touch Tone models.  Any Northern or Western 3 slot that has a switchhook/transfer contact assembly can have a modified single coil coin relay/ hopper and a controller board installed in it - even if it wasn’t originally pre-pay. 

In Post-pay Westerns (like a 210 or a 212) there’s no SL screw terminal.  It was replaced with two solder terminals that have the post-pay hopper wires connected to them.  If you disconnect the wires and solder a jumper between these terminals, they become the SL connecting point for the controller.

As an example, a Western Electric 193G is a great old dial payphone dating back to the late 1940’s and early 1950’s.  It has an F handset and self-contained ‘talk circuit’.  Unfortunately it’s nothing but a ‘piggy bank’.  Install a new style hopper/modified coin relay with a controller board and it becomes an animated, interesting phone that you’ll actually go out of your way to use.

Hearing the sounds of and watching the coins drop into the open return chute of a 3 slot payphone is part of our history and one of the pleasures of collecting antique telephones.  In my imagination I see Jackie Gleason using one of those payphones in countless episodes of ‘The Honeymooners’.

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                           Installation In An Automatic Electric 3 Slot

The controller board and modified coin relay/ hopper can be installed in any Automatic Electric LPA, LPB or LPC 3 slot.  It doesn’t matter if it’s Prepay, Semi Post-pay or Local-Prepay. You can even install the controller in the 3 slot 10 or 12 button Touch Tone models.

However, unlike Western Electric, some Automatic Electric payphones are more difficult to work with than others.  Some models performed functions internally that allowed them to be connected to normal subscriber phone lines, rather than dedicated coin lines.  This made them more complicated to work with and modify.

Be careful!  Although they look alike, the single coil Automatic Electric hopper is less deep than the Western or Northern Electric.  An Automatic Electric hopper will fit in a Western Electric.  A Western Electric won’t fit in an Automatic Electric.  Make sure you get a single coil hopper that was made by Automatic Electric.  It’s impossible to tell the difference by eye; they are that close in size.  I learned that the hard way!

Automatic Electric used a completely different technique than Western and Northern Electric to make their payphones $.10 initial deposit.  It’s not possible to use these $.10 Automatic Electric electromechanical assemblies with the controller board and the reduced coin relay trigger voltage. Unfortunately these payphones can only be $.05 initial deposit.

Of course you can still deposit any coin, nickel, dime or quarter, to bring up a dial tone, but the phone won’t be able to count the nickels like it did originally.

 You must deposit a coin in the payphone to answer an incoming call.  The coin will be treated like an initial deposit for an outgoing call when you hang up.

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Preliminary Tests

1-    Make sure your payphone is working properly. That means:

A- It brings up a dial tone when you go off-hook. 

B- It dials properly. 

C- You can carry on a conversation. 

D- It disconnects when you hang up the handset.

2-    The wiring may not (and probably isn’t) 100% factory original.  However, certain wiring

MUST still be in place for the controller circuit to work.  To check this, the following measurements are made on the screws of the terminal strip in the phone with the phone disconnected from the phone line.

A-  Using an ohmmeter, check that there is continuity between R1, the fourth screw

from the top and L1, the top screw, when the receiver is on-hook.

B- The ohmmeter should read an open circuit between these two points when the receiver is taken off-hook.

C-   If you’re getting these readings the controller will work fine. If you aren’t the

payphone was either rewired, or is a very early model (pre LPA) that must be updated

in order to work with the controller.  This requires replacing the hook-switch with one having a different contact configuration and adding a connection to the R1 terminal.  This is a lot of work.  You might consider finding a newer model payphone to work with.

3-  If the payphone had a coin relay, all of the relay wiring must be removed.  If you’re starting with a pre-pay model like an LPB-82, this is very easy to do.  There are three wires going to the coin relay. Tape and store each one.

Automatic Electric made so many different types of coin relays that it’s impossible to give specific instructions on doing this for each one.  You will have to physically look at the contacts and figure out what to short or disconnect to completely remove the coin relay and still have a working phone.

Assuming that:

1-    You removed the old coin relay, relay wiring and hopper.

2-    The phone is still working.

3-    You got the proper readings in step 2a and 2b.

 You can continue installing the modified coin relay/ hopper and controller board.

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Installation

          Refer to the picture below.  This is an Automatic Electric LPB-82-55 with the old style hopper and double coil coin relay removed.  The three wires that are hanging loose above the tray were connected to the old relay.  They can be taped and stored.

Refer to the picture below.  Install the modified coin relay/hopper in the phone.  Mount the controller board on the back casting with double-sided foam tape.  Connect the wires as follows:

1-    Lead Y from the controller board goes to L2 on the terminal strip. L2 is the THIRD screw down from the top.

2-    One side of the phone line also goes to L2.

3-    Lead SL from the controller board goes to R1 on the terminal strip. R1 is the FOURTH screw from the top.

4-    One side of  jumper ‘L’ goes to L1 on the terminal strip. L1 is the TOP screw. Jumper ‘L’ is an added wire with a spade lug on each end that is 12 inches long. We talked about making this jumper in the section at the beginning of the article on wiring the pc board.

The picture below is a close-up of the coin relay screw terminals.  All the remaining wiring will terminate on these screws.  They are:

A- The other side of the phone line connected to coin relay Terminal G.

B- The other side of the L jumper connected to coin relay Terminal 1.

C- The controller wire 2 connected to coin relay Terminal 2.

D- The controller wire 3 connected to coin relay Terminal 3.

E- The yellow jumper with the lug (from the other side of the relay) is also connected to

     Terminal 1.

          That makes a total of 5 leads with spade lugs that go to the screw terminals of the coin relay.

            This wiring is identical to the wiring of the coin relay terminals in the Western Electric installation.

Below is a diagram of the controller connected to an Automatic Electric 3 slot Payphone.

          Refer to the picture below.  The device in the top mounted to the coin track that was used for 2 nickel initial deposit will not work with the modified coin relay and the lower trigger voltage.

Rather than taking it out of the phone, it’s very simple to disable.  Move the wire spring out of its original position and put it on top of the assembly.  The phone is now permanently $.05 initial deposit.

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Final Testing

        Final testing an Automatic Electric payphone is identical to a Western Electric.  Except for one small difference.  To test a Western Electric with the top separate from the bottom, you had to make 5 jumper wires 2 feet long with spade lugs on each end.  For an Automatic Electric you’ll have to do a little more work.

You will make seven ‘clip leads’ 2 feet long with insulated boots on each end.  Radio Shack stocks the small alligator clips and the insulating boots. They also probably have flexible test lead wire.  At one time they sold pre-made clip leads.  I haven’t seen them in the stores for years.

                                                          http://tinyurl.com/ygflrk

If you plan on ordering the parts for the controller from Jameco Electronics, and you’ll be working on Automatic Electric payphones, they sell a package of pre-made clip leads. The part number is #10444CG.

                 http://www.jameco.com/Jameco/catalogs/c264/P304.pdf

Since the Automatic Electric phones have flat contacts and no screws to attach spade lugs, this is the only way this can be done.

          There was a test cable made by Automatic Electric for this purpose.  I know of two that exist.

A friend of mine has one.  The second one he gave me as a gift.

A picture of the test cable connected to the completed LPB 82-55 is shown below.

IT’S GREAT HAVING FRIENDS!

Hopefully you made the clip leads and you can work on the phone with the top separated from the bottom.

1- Plug the phone into the line.

2- Lift the handset.

3- Drop a coin down the throat of the hopper.

4- You should hear a dial tone.

5- Try the dial and make sure you can break dial tone.

6- Hang up the phone.

7- The coin relay will snap closed.

8- The coin will immediately return or collect. Whatever you set it to do.

9- Two seconds later the coin relay will disengage.

 In order to answer an incoming call a coin must be deposited after the handset is lifted.  Any coin will work.  To keep the design of the controller as simple as possible, incoming calls had to be handed this way.

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The End?

          I realize that this article seems to go on forever.  I tried to foresee any complication or confusion in modifying the coin relay and hopper.  I also attempted to answer any questions before they became an issue.

These payphones were made in many different models, having interchangeable parts, by a few different manufacturers over a long period of time.  Yes, they can be very confusing.

          When you start the actual ‘hands on’ part of this project, you will find that it will go very quickly.  It appears more complicated than it really is.

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A Final Thought

          Given the lack of complexity of the circuit, the nominal cost of material and the simple installation, you will be amazed at how much is being done by so little.

Now, unplug the clip leads.  Put the top on the phone and lock it up.  Get a handful of change and enjoy playing with your new toy. 

Now, go clean up the mess you made building all this!

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