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Old 2nd Nov 2019, 9:30 am   #1
raducosma
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Default DTMF to pulse converter

Hi, I'm new here and I hate to start with a question, but I do need some help.

I'm looking for a DTMF to pulse converter (yes, not the other way around); my goal is to link a DTMF-only device to an intercom system that uses pulse dialing.
I already found an old thread here, suggesting to use an Mitel SmarT-1, which I just ordered and waiting to be delivered.

But what I would really like to do, for the sake of simplicity, is to use a smaller device dedicated for this job.
Digging up online I found references of interface converters from CTC and Lanode, but information is scarce.

So my question is: does anyone know where I could find such devices, or something similar?
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File Type: pdf DTMF to pulse converter.pdf (23.7 KB, 199 views)
File Type: pdf CTC_Union_2009_Product_Catalog_p161.pdf (330.5 KB, 126 views)
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Old 2nd Nov 2019, 12:43 pm   #2
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Default Re: DTMF to pulse converter

Doesn't seem to be in their latest catalogues
Here in the UK you have to be careful when acquiring some Mitel SMarT-1s as they have firmware specific to a certain telecoms provider and always prefix anything dialled with their networks access digits.

Luckily I've got several 'DTMF 2 Pulse' converters that were designed to do the trick that we produced. I've also got some ex-British Telecom 'Signalling Converters 43A' which were used in public exchanges to give the ability for users to have a DTMF telephone on an exchange that only accepted pulse dialling. They were a product produced in the USA. But date from way back in the 1980's - I recovered mine from Cheetham Hill exchange in Manchester in the mid-1990's after the exchange had been converted to digital working.

I administer a worldwide network for collectors of old telephone systems and telephones working over the internet using VoiP to connect the old equipment - no line rental or call charges! There are many pulse dialling only systems connected and many folk achieve the conversion using an early electronic PABX such as the Panasonic KXT systems which can now be picked up cheaply on eBay. When you say 'intercom' I assume that you mean a 'Private Automatic eXchange (PAX)' ?

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Old 2nd Nov 2019, 4:25 pm   #3
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Default Re: DTMF to pulse converter

Thanks for the reply.

Yes I've read that some SMarT-1s can be locked to specific providers, but I decided to take my chances, seeing how it's the only option I could find so far. There's still a long way to go, programming the unit.

About signaling converters, do you happen to know anyone who is willing to sell one of these small boxes?

By 'intercom' I mean the door phone used in my apartment building. I don't know exactly how it works, but what I do know is that it needs a pulse-dialing phone to pick up and press a specific key to unlock the door.
If I can get it working with a DTMF phone, ultimately I want to hook up an invoxia Voice Bridge and use it to let myself in the building using my mobile pone, no key, nothing else.

P.S. I think I accidentally stumbled upon a post mentioning your private network at one point, while frantically searching for how to convert tone to pulse.
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Old 2nd Nov 2019, 8:26 pm   #4
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Default Re: DTMF to pulse converter

That is really tricky, (Ian has learned me the most of what I know about this. )
I have had trouble programming the Mitel Smart ones, and it is differences between those made for US and UK when it comes to programming. Maybe it is just luck, but I have now one up running for 4 phones, but I convert the other way, rotary to DTMF, but that should not be the big problem.
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Old 3rd Nov 2019, 10:03 pm   #5
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Default Re: DTMF to pulse converter

Hi, From experience the Mitel Smart T1 may be your only option these days for Tone to pulse conversion.
There are a number of PBX's available that do pulse to tone, however I'm not sure about the "other way round" as it were and physically they may be a similar size or larger than the Mitel smart dialler.

The Mitel Smart T1 can be programmed from a standard DTMF phone, the only thing I have experienced is that they don't seem to like digit strings of less than three digits - I'm not certain whether I may have a setting incorrect in mine though which could be causing that.

Regards

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Old 3rd Nov 2019, 11:55 pm   #6
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Default Re: DTMF to pulse converter

Quote:
Originally Posted by AndiiT View Post
There are a number of PBX's available that do pulse to tone, however I'm not sure about the "other way round" as it were...
I don't know about more modern PABX offerings (where loop disconnect (pulse) dialling may be deemed unnecessary), but my London 16, which accepts either DTMF or LD dialling from its extensions, has links on its exchange cards to select either DTMF or LD for each exchange line.

Also, the instructions for the Revelation states that exchange lines can be individually programmed to provide either DTMF or LD dialling, though I have not tried this on mine.
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Old 4th Nov 2019, 11:38 am   #7
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Default Re: DTMF to pulse converter

Without knowing too many specifics of what you want to achieve, but couldnt you use/adapt something like this

ebay 283444893395

https://www.ebay.co.uk/itm/DTMF-deco...4AAOxyFd1SJcA~

Might need modifying, and the PIC will need re-programming to store the recieved tone codes, and then pulse the relay depending on the detected tones.
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Old 4th Nov 2019, 9:45 pm   #8
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Default Re: DTMF to pulse converter

Thanks everyone for the feedback.

The SMarT-1 should arrive soon and I can start programming it. Indeed, it seems like one of the smaller choices compared to other devices, although not ideal.

@PETERg0rsq that does seem like it could do the job, at least technically, but re-programming the PIC is too much for me.

At this point I'm just looking for a compact, ready-made, interface converter, like the CTC unit which is 135x79mm.
If anyone can give me some clues about where to look for one, or perhaps a part number to search for, I'm looking forward.
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Old 5th Nov 2019, 5:42 pm   #9
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Default Re: DTMF to pulse converter

Quote:
Originally Posted by raducosma View Post
By 'intercom' I mean the door phone used in my apartment building. I don't know exactly how it works, but what I do know is that it needs a pulse-dialing phone to pick up and press a specific key to unlock the door.
If I can get it working with a DTMF phone, ultimately I want to hook up an invoxia Voice Bridge and use it to let myself in the building using my mobile pone, no key, nothing else.
Are you sure the intercom uses a pulse dialling (10 pps) PSTN type phone? Most use a 5-wire system with separate wires for talk, listen, buzzer and lock (and common).

If you want to wire a DTMF-controlled relay contact across the intercom lock release button, something like

https://quasarelectronics.co.uk/Item...relay-switcher

https://www.velleman.eu/products/view/?id=9321
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Old 5th Nov 2019, 9:11 pm   #10
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Default Re: DTMF to pulse converter

I am sure (unfortunately), otherwise it would have been much easier.

The indoor unit provided is a bog-standard phone that you pick-up to answer/talk and press 0 to unlock.
I replaced it with an old cordless phone that can do pulse dialling and it just works.

Thanks for the suggestion though.
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Old 12th Nov 2019, 11:45 pm   #11
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Default Re: DTMF to pulse converter

I just received the Mitel SMarT-1 today and started playing around with it.

Following the manual, and using a terminal connection, I managed to reload factory defaults and configure ports 1 and 2 as "Loop Start, Rotary", while leaving ports 3 and 4 in MF4 mode.

I have the supposed "exchange line" connected to port 1, and a couple of phones connected to ports 2 & 3 in Pulse and Tone mode respectively.

Is there something specific that I need to configure in order to "link" the exchange line (port 1) to the phones? (so that an incoming call will ring phones connected to ports 2 & 3)
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Old 14th Nov 2019, 8:05 pm   #12
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Default Re: DTMF to pulse converter

Quote:
Originally Posted by raducosma View Post

Is there something specific that I need to configure in order to "link" the exchange line (port 1) to the phones? (so that an incoming call will ring phones connected to ports 2 & 3)
You can't.
The Mitel Smart1 is not a PABX, it is four separate Alternative Carrier Routing devices in one box. We used to call it Least Cost Routing, but that might have been disingenuous, depending on who was sponsoring the installation

Using a single channel should however do what you want DTMF>pulse.

These weren't the easiest things to programme manually back in the day, I became quite proficient, but unfortunately lost all my hand written notes a decade ago.

Where is this forum thread you are using?
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Old 14th Nov 2019, 9:30 pm   #13
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Default Re: DTMF to pulse converter

The full horror of these things is coming back to me now
http://www.wedophones.com/Manuals/Mi...1%20Dialer.pdf
No wonder I made copious notes with UK specific examples for the various carriers we used. Getting the polarity of a trunk reversed could cause mis dialling, and make payphones demand money with menaces! But I digress.

You must have successfully "star initialised" and woken up the controller, by setting a line to pulse rather than the default DTMF, that is the "line" or "CO" side, so is correct for your door opener.

I think the phone side is always dual DTMF/Pulse so should accept what ever the phone uses without configuration.

The defaults are USA specific:

Set all trunks to loop start, DTMF **You have changed this to rotory/DP on line 1**
Route all non 1 + (local) calls go via DDD
Route all 911, f-411, l-555, l-area code-555, l-800 calls go via DDD
Route all other l+ (long distance) calls go via OCC
Route all local calls after the first digit is dialed
Route all l+ calls after fourth digit dialed.

So you need a DP "0" to open the door-latch, what happens to the CO side when you dial a single "0" on your DTMF phone?
What about a string of "0s"
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Old 14th Nov 2019, 10:51 pm   #14
raducosma
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Default Re: DTMF to pulse converter

Thanks for the reply.

Perhaps I misunderstood what the SMarT-1 is capable of, or more precisely what it was designed to do.
I was under the impression that I could configure it to allow one DTMF-only phone to access (dial out and receive "calls") on a pulse line.

I'm not sure I understand what you mean by "using a single channel", but it sounds hopeful. Could you please elaborate?

Right now, when I dial a single 0 on my DTMF phone, nothing seems to happen. Same for a string of 0s. Normally I should hear the pulses in the earpiece and the door would unlock.
For testing, I simultaneously connected a pulse phone on another port (configured as pulse), but that one also doesn't seem to do anything.
Additionally, "calling" from the outside does not produce any ringing on the phone.

Maybe I'm not doing the connections right, since you say it's not a PABX...
I basically just connected the line ("CO side") to port 1, and the test phones to ports 2 and 3.

Last edited by raducosma; 14th Nov 2019 at 10:56 pm.
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Old 14th Nov 2019, 11:11 pm   #15
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Default Re: DTMF to pulse converter

If you were able to initialise the system and do some programming (and hear the confirmation beeps) you must have had your phone connected to the correct pair of pins on one of the RJ45 ports. Moreover, you must also have had a telephone line, or your door-phone system connected to the remaining pair of pins on the same port That's what I meant by the same channel, the same RJ45

In theory, four apartments could each use a port, but you only need one.
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Old 14th Nov 2019, 11:32 pm   #16
raducosma
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Default Re: DTMF to pulse converter

Actually, I did all programming from a computer, using a serial/console cable. This is what I meant by "terminal connection"... command line terminal. I used to be a network engineer, so this is more familiar to me than dialing on a phone

I did not connect the phone and the line on the same port; perhaps this is my mistake... is there a diagram/pin-out for wiring a phone and line to the SMarT-1? The manual seems pretty vague.
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Old 14th Nov 2019, 11:52 pm   #17
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Default Re: DTMF to pulse converter

Ah, I should have realised!
What you have to remember that when I was working with these 30 years ago, a company laptop was a distant dream!

However I've given your project some thought and things might not be quite so straightforward.
You asked for a device that could convert DTMF to DP and the SMART-1 will do that, but it is designed for originating phone calls.

As I see it, you will effectively be receiving a call, so the sequence will be
Visitor calls you and your phone rings
You pick it up and speak to the visitor
you dial 0 and the door is unlocked

I guess you will have to briefly hang up and seize the line afresh before pressing the digit, but apart from that it should work.
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Old 15th Nov 2019, 12:19 am   #18
raducosma
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Default Re: DTMF to pulse converter

That's right, the normal process is like you describe it:
1. Visitor calls you and your phone rings
2. You pick it up and speak to the visitor
3. You dial 0 and the door is unlocked

Step 1 is actually optional. Normally the system allows me to just pick up the phone (go off hook) and just dial 0 to unlock the door, without anyone initiating the "call".

So, could you please explain how do I need to wire the phone and line on the same RJ45 or RJ11? Do they need to go on the same middle pins, or on separate pairs of pins (and which ones)?

The manual is scarce, or perhaps it's addressed to someone with basic knowledge about wiring up a system like this.
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Old 15th Nov 2019, 11:00 am   #19
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Default Re: DTMF to pulse converter

You are right, the manual does not make it clear, I do remember however that the phone and line pairs are side-by-side, and not outer - inner. So you only have two permutations to try.
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Old 15th Nov 2019, 8:01 pm   #20
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Default Re: DTMF to pulse converter

Quote:
Originally Posted by raducosma View Post
That's right, the normal process is like you describe it:
1. Visitor calls you and your phone rings
2. You pick it up and speak to the visitor
3. You dial 0 and the door is unlocked

Step 1 is actually optional. Normally the system allows me to just pick up the phone (go off hook) and just dial 0 to unlock the door, without anyone initiating the "call".

So, could you please explain how do I need to wire the phone and line on the same RJ45 or RJ11? Do they need to go on the same middle pins, or on separate pairs of pins (and which ones)?

The manual is scarce, or perhaps it's addressed to someone with basic knowledge about wiring up a system like this.
Telephone is connected to 'Subscriber' and 'Exchange' is connected to 'Telecom' - hence connect your telephone to 'Subscriber' and the Door Unit to 'Telecom' making sure that you use the same two numbers i.e. 'Subscriber 1' and 'Telecom 1' . The 'incoming' ring should go straight through the unit for an 'incoming call'.
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