Built a payphone controller for WE 233G

[john snapp]

For a while I had been planning on finishing a payphone controller I made for a Western Electric 233G payphone.  My requirements were that I wanted it to appear to the user to work as closely as possible to the original 3 slot payphones.  I also wanted it to collect and return the money not based on a timer but on far end answer supervision.  While this is difficult to get on a POTS line, it is possible to get answer supervision with Voip lines.  While I originally use a Grandstream ATA adapter, I eventually switched to the far superior Audiocodes MP-118.  These are 8 line ATA that provide 8 FXS loop start ports.  You can usually fine then on ebay used for about $75.  My voip line costs me about $1.50 a month for each phone number and about $0.0012 a minute for phone calls.  All the lines can share one DID number if you do not want different numbers to call the phone.  The paystation I used was a standard WE 233G that was converted back to original wiring and specifications.  I also used a 655A subset.  I built the pay phone controller on a bread board at first then spun a circuit board for it.  The controller had a capacitor multiplying circuit that took 22VAC and gives me 100V DC to activate the coin relay.  It also has a ground start line simulator so that it can act like a ground start and then switch over to the loop start ATA when a coin is detected and the phone is off hook.  There are also circuit to detect forward and reverse line voltage for off hook detection and answer supervision and a ring detector to allow for incoming calls.  I threw a small cheap Arduino nano microcontroller to do what relays did so elegantly and efficiently 60 years ago.  Comments and feedback is welcome.

I have a few questions for folks though on timing.  I believe that originally when you picked up the phone before depositing a coin there was no dial tone since this was a ground start line and the coin was the ground start trigger.   When you deposited a coin, you would get a dial tone.  Was there any delay before you got a dial tone or was it almost immediate?

When you hang up, I understand there was often a delay before the coin was collected or returned.  How long was this delay.  I think I have it set at 2 seconds ring now but have no idea what it originally was.  Was it the same delay for a collect and a return?

I all need to do now is create a AI Bot to act like a long distance operator. 

Here is a youtube video I made that walks you through what I did.


https://youtu.be/LFy2D-u5Su4

[.....]

Very cool, job well done!

[rcourtney]

On SxS the ground start delay was the same as loop start. 200-300ms.

900ms typical for applying coin voltage.
There was usually a coin test to see if coin was properly disposed of after applying coin voltage.

Coin tones were not present on 3 slotters but instead a mic placed on the coin pathway would hear the bell and chime.
You can look for a spike in return audio
using a high and low bandpass filter.

I have only tested with modern payphones.

[Payphone installer]

So nobody answered you question about the delay on hangup. It was about two seconds. It is not important as to what you use to produce dial tone as your goal is not to allow the phone to have access to the dial tone until the initial rate is satisfied.this is accomplished by applying ground on the tip side of the line to a device that allows the dial tone into the phone. When it sees the tip ground you can dial.