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'[EE]:Telephone System Simulation'
2002\08\27@154713 by Tim McDonough

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I'm working on a project where a device with an internal modem needs to be tested in an environment where it will share a telephone line with other devices like telephones, fax machines, credit card machines, etc. Anyone have first hand experience with testers/simulators that can be programmed to produce phone line conditions such as other devices being off hook, etc.?

Tim

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2002\08\27@160331 by Richard Sloan

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I used some equipment from Teltone at one time and it was very nice.

http://www.teltone.com

Richard.

>>  I'm working on a project where a device with an internal modem needs to be
>>  tested in an environment where it will share a telephone line with other
>>  devices like telephones, fax machines, credit card machines, etc. Anyone
>>  have first hand experience with testers/simulators that can be programmed
>>  to produce phone line conditions such as other devices being off hook,
>>  etc.?

>>  Tim

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Thanks,
Richard Sloan
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2002\08\27@161205 by Andrew Warren

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Tim McDonough <.....PICLISTKILLspamspam@spam@mitvma.mit.edu> wrote:

> I'm working on a project where a device with an internal modem
> needs to be tested in an environment where it will share a
> telephone line with other devices like telephones, fax machines,
> credit card machines, etc. Anyone have first hand experience with
> testers/simulators that can be programmed to produce phone line
> conditions such as other devices being off hook, etc.?

   I'll echo Richard Sloan's recommendation of Teltone products.
   Teltone's on the web at:

       http://www.linesimulators.com/

   -Andy

=== Andrew Warren -- aiwspamKILLspamcypress.com
=== Principal Design Engineer
=== Cypress Semiconductor Corporation
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

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2002\08\27@161615 by Jim Main

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Why not buy an inexpensive home telephone exchange?  (say one-line 4
extension) - you might be able to pick one up second hand even.

Jim

{Original Message removed}

2002\08\27@230555 by Katinka Mills

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> -----Original Message-----
> From: pic microcontroller discussion list
> [.....PICLISTKILLspamspam.....MITVMA.MIT.EDU]On Behalf Of Tim McDonough
> Sent: Wednesday, 28 August 2002 3:44 AM
> To: EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU
> Subject: [EE]:Telephone System Simulation
>
>
> I'm working on a project where a device with an internal modem
> needs to be tested in an environment where it will share a
> telephone line with other devices like telephones, fax machines,
> credit card machines, etc. Anyone have first hand experience with
> testers/simulators that can be programmed to produce phone line
> conditions such as other devices being off hook, etc.?
>
> Tim

If you were in Perth Au, I would say come on over lol I have PABX's of most
types, from the newer 12V line 50V ring to the older 48V line 115v ring :o)
(I hate KSU phones, I love old uP based exchanges, I have an Ericsson AXE
exchange in storage (anyone want to set up a community exchange ? (these
were the last ones used by our telco (Telstra)) It fell off a truck, and the
insurance company said it would cost more to repair than it was worth, SO I
bought it at auction, and apart from a few ripped connectors, dents and
scrapes in the caseing, it runs fine.

I would not blindly use a home PABX, untill I had verified that it has a
48Vdc line. I would also use an LCR network, to simulate some line length
(unless you have a few Km's of cable). I have had equipment work fine 2ft
from the exchange, but 10 - 20Km away and the line was not capable of
powering it :o( LCR networks are the best for simulating line lengths. If
you need info on calculating the LCR values for given line lengths I can dig
up the formula (it is provided in the AU phone regs (the one set of regs
cover aproval as well as instalation lol)

Regards,

Kat.

**********************************************
K.A.Q. Electronics.
Electronic and Software Engineering.
Perth, Western Australia.
Ph +61 (0) 419 923 731
**********************************************

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2002\08\27@234340 by Tim McDonough

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On Wed, 28 Aug 2002 11:01:50 +0800, Katinka Mills wrote:

>If you were in Perth Au, I would say come on over lol I have PABX's of most
>types, from the newer 12V line 50V ring to the older 48V line 115v ring :o)

That's certainly a kind offer but getting the travel approved could be tricky!

>I would not blindly use a home PABX, untill I had verified that it has a
>48Vdc line. I would also use an LCR network, to simulate some line length
>(unless you have a few Km's of cable). I have had equipment work fine 2ft
>from the exchange, but 10 - 20Km away and the line was not capable of
>powering it :o( LCR networks are the best for simulating line lengths. If
>you need info on calculating the LCR values for given line lengths I can dig
>up the formula (it is provided in the AU phone regs (the one set of regs
>cover aproval as well as instalation lol)

My concern is that there's some evidence in early tests that the internal modem can't detect when the line is already in use if there are either quite a few phone instruments on the line and especially if there are a few extensions that are really "cheap" telephones. Line length may be a factor too as you suggest.

Anyway, it's an interesting problem to work on. Keeps the job fun.

Tim

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2002\08\28@101522 by Marc Joffe

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At my work we use a device called an Abacus, which is manufactured by Zarak
http://www.zarak.com

This may be overkill for what you are doing as I am not exactly sure what
kind of load you need to generate. Our configuration pumps out more than
12000 calls per hour over 750 trunks.

I know that the smallest system costs around $10 000 so this may be
overkill for your project.

Marc

At 02:43 PM 27/08/2002 -0500, you wrote:
{Quote hidden}

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2002\08\28@111824 by Tim McDonough

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On Wed, 28 Aug 2002 10:19:23 -0400, Marc Joffe wrote:

>This may be overkill for what you are doing as I am not exactly sure what
>kind of load you need to generate. Our configuration pumps out more than
>12000 calls per hour over 750 trunks.
>
>I know that the smallest system costs around $10 000 so this may be
>overkill for your project.

Definitely overkill but it does sound pretty cool for the right application.

Tim

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2002\08\28@143732 by Peter L. Peres

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On Tue, 27 Aug 2002, Tim McDonough wrote:

>My concern is that there's some evidence in early tests that the internal
>modem can't detect when the line is already in use if there are either
>quite a few phone instruments on the line and especially if there are a
>few extensions that are really "cheap" telephones. Line length may be a
>factor too as you suggest.

This is a well known problem. The fix in our case is external. It involves
wiring a zener diode across a small rectifier bridge and putting it in
series with the line to the 'insensitive' modem. 7V2 worked here before.
You can bypass the bridge with 0.1uF if you are nervous. This is not
really necessary.

You could build this into your circuit (or desensitize the line voltage
sensing opto using a small zener diode or resistors).

Peter

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