Author Topic: Spanish Payphone, I need help to make a controller  (Read 11963 times)

Offline Jack Ryan

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Re: Spanish Payphone, I need help to make a controller
« Reply #15 on: December 07, 2013, 05:39:45 AM »
Dsk,

The low coin indication is probably the coin window; I can't see how the exchange would know that there in no coin available for the next coin collection.

My thoughts on the C contact:

When there are no more coins, contact C is closed stuffing the 5k section of the coin relay. When the next reversal happens, there is a much larger current drain telling the exchange that there is no coin and the connection is ended.

Regards
Jack

Offline Spanish_phones

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Re: Spanish Payphone, I need help to make a controller
« Reply #16 on: December 07, 2013, 08:27:11 PM »
This phone show one more secret each time I open it! I have discover the two coils that where on the diagram and I didn't know where they were (pictures below)

Also I have made a polarity switch, and it works! The relay collects the tokens one by one! And I think I guessed how the call is ended when there are no tokens left. If you continue with the polarity reversed, then you don't have dial tone, that means the call is ended.

I think the most difficult feature would be the first token collected, when the party answers, I have no clue to make it. The other things should be easy: a circuit with two relays, for changing the polarity, and the electronic circuit for timing and operate the relays. I think the controller should work with the 6V DC of the telephone line.

I think I could do the relay circuit myself, but I don't know anything about electronics, so I need help in that part of the circuit, the timer.

;)


Offline dsk

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Re: Spanish Payphone, I need help to make a controller
« Reply #17 on: December 08, 2013, 04:20:07 AM »
I have been looking at some different systems, and you do not get a signal indicating answer in the other end, except for lines with polarity reversal. The only way to get this is by using an ATA and voip. The timer circuit will be an additional thing. The polarity reversal are at least mentioned in this thread:   http://tinyurl.com/nw293d2

The controller circuit might be a complex thing, and the only way I could solve it will be with a PLC and that's unreasonable expensive. 

Some other people at the forum has mad other controllers, and might help.

dsk

I have even got a regular New York number :-) 646 570 1796

Offline Jack Ryan

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Re: Spanish Payphone, I need help to make a controller
« Reply #18 on: December 08, 2013, 04:24:18 AM »
My thoughts on the C contact:

When there are no more coins, contact C is closed stuffing the 5k section of the coin relay. When the next reversal happens, there is a much larger current drain telling the exchange that there is no coin and the connection is ended.

I didn't say so explicitly but I believe that the reversals are fleeting. Each fleeting reversal collects a token and when no tokens remain, the last fleeting reversal terminates the call.

Jack

Offline dsk

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Re: Spanish Payphone, I need help to make a controller
« Reply #19 on: December 08, 2013, 04:46:30 AM »
I have just been looking for timers, and this one: http://tinyurl.com/q3fdfjp may be good enough.
My idea are: If a polarity sensor (diode and relay, or indicator contact C ) tells when the ATA reverses the line, (first token are collected) the timer starts, and after some time it gives another relay signal to reverse polarity. (2 contact sets) and breaks the timer current.  The relay will loose its current, normalize polarity, and start the counter again.
This will keep on until hanging up.

This is just an idea, and I do not know if it will work for real.

dsk

I have even got a regular New York number :-) 646 570 1796

Offline G-Man

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Re: Spanish Payphone, I need help to make a controller
« Reply #20 on: December 08, 2013, 05:07:21 AM »
It most likely would be an extremely simple task to inexpensively emulate the original metering pulses with a timing circuit derived from a 555 or similar i.c. driving an equally inexpensive polarity reversing relay at regular intervals. 

I suspect the circuit could be constructed for under $20.00.

Offline dsk

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Re: Spanish Payphone, I need help to make a controller
« Reply #21 on: December 08, 2013, 08:40:32 AM »
Very creative switch:

If you add a function able to stuff the line (doorbell-switch)

I would like to ask you to make a test.

1- With normal polarity (able to dial) listen for dial tone, put inn some tokens, and dial ( at least 1 digit)
2- Reverse polarity (and leave it reversed)    Do it collect 1 token? Are you still holding the line, able to hear yourself (transmitter working)?
3- press and release the doorbell switch.  Does it collect one more token? Whats happening?
4- Hang up. Does it return the unused tokens?
5- Switch back to normal polarity. Nothing should happend, or???

dsk

I have even got a regular New York number :-) 646 570 1796

Offline Jack Ryan

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Re: Spanish Payphone, I need help to make a controller
« Reply #22 on: December 08, 2013, 06:02:49 PM »
Dsk,

Do you disagree with my suggestion or have you not noticed it?

Jack

Offline Spanish_phones

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Re: Spanish Payphone, I need help to make a controller
« Reply #23 on: December 08, 2013, 10:56:37 PM »
Dsk, I'm afraid I cannot make the test you asked me until I make a two relay switch circuit, because the manual switch that I made doesn't work properly and it's really slow. With a fast relay reversal should work just has you said.

Just for clearing doubts:

For collect a token: only changes the polarity less than a second, then it must return to normal polarity yo hear the conversation

I don't know the function of contact C jet, but I think call must end at the las polarity reversal, NOT returning to normal polarity, so you cannot hear dial tone neither the conversation.

;)

Offline dsk

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Re: Spanish Payphone, I need help to make a controller
« Reply #24 on: December 09, 2013, 02:25:39 AM »
Dsk,

Do you disagree with my suggestion or have you not noticed it?

Jack


No, I'm pretty sure you are right, but it might be a minor possibility of just a stuff, or power loss will do the job, but that's depending on a working state with reverser polarity during conversation. (current goes trough the 100 ohms coil.) 

dsk

I have even got a regular New York number :-) 646 570 1796

Offline Jack Ryan

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Re: Spanish Payphone, I need help to make a controller
« Reply #25 on: December 09, 2013, 05:14:06 AM »
Dsk,

I don't claim to be right, I just wanted to bounce some ideas.

The circuit is hard to read because all the contacts look like hook switch contacts. I am just assuming that L and C are token contacts and that with a token present, L opens and C closes. Can this be checked by observation?

If that is the case, I had it the wrong way around:

- Each fleeting reversal collects a token unless there is no token
- If there is no token, the exchange sees a high impedance (5k1) loop on the fleeting reversal and terminates the call.

I don't think the high impedance for the duration of a fleeting reversal is sufficient to terminate the call in itself; the exchange would have to look for it.

Jack

Offline Spanish_phones

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Re: Spanish Payphone, I need help to make a controller
« Reply #26 on: December 09, 2013, 08:07:23 PM »
Well, here you are a few answers to your posts.

First, a photo of the contacts L and C. L permits to dial, I think C should end the call when the last token is collected. They work separately, but together, in other words, the position of L doesn't affect on C and viceversa, the work independently.

I've also made a video of how the system should work:

http://youtu.be/bSDMtUCeMBs

As you can see, collecting one token requires two movements, only one pulse/reversal, which make the first movement, then when the current returns to normal polarity, a spring pulls the big coil back. In the video, the last token collected gets stuck, leaving C contact closed and L contact open, so this combination should end the call ( when there are more token left, L contact is open by the next token)

I'm afraid reversing the polarity is going to affect on the quality of the call, or even end it. Maybe I have to develop a device that sends negative pulses to the telephone, in order to control the collect system without ending the call meanwhile? Anyway, I think I'll make a test with the two relays reversing polarity and see if it works or not. Does anybody know were can I buy relays?

Thank you so much ;)
« Last Edit: December 09, 2013, 08:14:35 PM by Spanish_phones »

Offline Jack Ryan

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Re: Spanish Payphone, I need help to make a controller
« Reply #27 on: December 09, 2013, 09:08:00 PM »
Thanks for the additional picture.

I don't want to labour the point but I'd like to ask some more questions.

The L and C contacts are physically separated and so won't work in unison (at the same time). With no tokens inserted, L is closed and C is open.

1. What is the state of L and C with one token inserted.
2. What is the state of L and C with two tokens inserted.

In the two step collection process (reversal and then return to normal), does the token move with the reversal, pause and then fall into the collection box when the voltage returns to normal?

There must be a reason that the L and C contacts are physically separated and that reason will be part of the explanation for call completion.

Thanks for that.

I am surprised that I can't find any information from Standard Electric or the Spanish telephone operating company regarding the operation of their payphones. Has anyone else had any success?

Jack
 

Offline Jack Ryan

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Re: Spanish Payphone, I need help to make a controller
« Reply #28 on: December 10, 2013, 12:03:34 AM »
Iñaki,
I think your video has answered some of my questions.

1.   With no tokens inserted, L is closed and C is open.
2.   When a token is inserted, L opens and C remains open
3.   When the reversal happens, the token moves forward and C closes stuffing the 5k section of the coin relay so the exchange sees a low impedance when a token is collected.
4.   When the voltage returns to normal, the token is collected and C opens.
5.   On the next reversal there is no token to move forward so C remains open. The exchange sees a high impedance telling it there is no token so the call in terminated.
6.   The line voltage returns to normal

So my guess as to how the phone works is as follows:

1.   Lift handset & get dial tone but the dial is disabled (Contact L is closed, stuffing the dial pulse contacts)
2.   Insert token(s) to enable dialling (Contact L opens)
3.   Dial the required number
4.   A fleeting reversal on answer takes the first token
5.   Subsequent fleeting reversals timed at the current charge rate collect additional tokens
6.   When there are no more tokens, a fleeting reversal is presented with a high impedance causing the exchange to end the call.

A fleeting reversal in this case is:
1.   A reversal
2.   A delay of 500 to 1000 ms (maybe even more) – enough for the token to move forward to close contact C and for the exchange to measure the loop impedance.
3.   A reversal to return the line polarity to normal.

If this is correct, a controller would not be too complicated. For example a Grandstream Networks, Inc. HT502 would give you pulse dialling and a line reversal on answer. The line reversal could be used to enable a timer to give fleeting reversals to collect coins.
The hardest part would be detecting the loop impedance when the token is collected and disconnecting the call when there is no token (a high impedance).

Is (was) this type of payphone common in Europe?

Thanks
Jack

Offline G-Man

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Re: Spanish Payphone, I need help to make a controller
« Reply #29 on: December 10, 2013, 02:28:49 AM »
“I'm afraid reversing the polarity is going to affect on the quality of the call, or even end it.”

Audible clicks were inherent with the Karlsson System Message Register Impulses, which is what your payphone relied on.

Here is an excerpt detailing this manifestation:

Quote
While the escrow coin station system allows for time
independent coin deposits, it has the disadvantage that
the metering pulses appearing on the loop during con
versation manifest themselves to the conversing parties
as annoying and disruptive audible clicks. To resolve
this problem the prior art has resorted to transmission
improvement techniques that serve to attenuate this
effect.

Note that it states that it can be attenuated; not completely eliminated.