[Asterisk-Dev] Raising loop current limit on the Proslic (reg.71)

[Alfred R. Nurnberger]

We are using the ProSlic in our products and found that some telecom
equipment
has problems dealing with 20ma loop current so we raised it to 30 ma and
some of our customers were much happier.
The only concern I would have are thermal problems with the driver
transistors when you raise the loop current
to the max 41 ma. Otherwise the Proslic is fine with 30 ma.

P.S there are quite a few more options of interest in the ProSlic worth to
be exploited.

i.e. The possibility to run cheap "hotel room phone" neon call waiting
lights. by programmming the ring voltage
     generator to output a very slow 0.5hz ring current (= 90vdc)
     or sending of 12 or 16kHz metering pulses which is quite common in many
countries.

Alfred R. Nurnberger
F L O S Y S
Making Communications Flow
Tel:  +1 (503) 972-9300
Fax:  +1 (503) 972-9309
US Toll Free: 1-877-4FLOSYS
http://www.flosys.com


-----Original Message-----
From: asterisk-dev-admin at lists.digium.com
[mailto:asterisk-dev-admin at lists.digium.com]On Behalf Of Rich Adamson
Sent: Friday, March 05, 2004 2:10 PM
To: asterisk-dev at lists.digium.com
Subject: Re: [Asterisk-Dev] Raising loop current limit on the Proslic
(reg.71)


>> > After I hit send I realized I was "out of context" with the original
>> > topic. For the central office based loops, the 12 to 30+ still holds
>> > true for many CO switches. There are still a large number of CO
switches
>> > that are not current regulated loops; those are still I=E/R with E
fixed
>> > at -48 and R varing depending on the distance. Try some 10 mile loops.
;)
>>
>> Yikes.  I was not aware of this.  Thanks for the note though, along with
>> Matteo's fixes for "heavier" loads for the TDM400P I think the archives
are
>> much better off for it all.  :-)

>Not that this has any real value, for grins I just checked one of our pstn
>lines. Stats: 51.8 vdc and 31 ma actual using a very old ITT desk phone.
>The short-circuit current (placing a ammeter directly across the tip/ring
>pair) was 37 ma, indicating the copper plant plus CO hardware was the
>equivalent of 1400 ohms.  I don't have a clue what gauge of copper plant
>the telco is using, but I do know we're on an electronic CO and within
>dsl distance. (26 gauge telco cable runs about 80 ohms per 1,000 feet.)

>So from that, its fairly easy to determine whether the central office has
>any form of current-regulated loop, and obviously in this case it does not
>(31 ma verses 37 ma). Pure educated guess is we're about 10,000 feet from
>the central office. I've not heard of any case where a central office
>provides current-regulated loops, but then I'm not in a position where I
>would have any need to hear about them any more. (They may exist, just
>don't have a real clue.)

>For someone that is located right next door to the central office, I'd
>expect to see about 70 ma while someone five miles from the office is
>likely to see about 15 ma (give or take a little depending upon how the
>copper was engineered, etc). There is no such thing as a 20 ma standard
>or telco objective in the US other then as a order of magnitude value.

Yes, some old offices on short loops put out up to 100ma.
Causes sometimes problems with electronic line cards.

Also sometimes boosters were installed which used an additional 24 or 48
battery supply ( makes a total of 72 - 96V open loop voltage) to provide
enough juice to run phones on very long loops.

So even the "standard" -48V is not always standard.

>As a side note, I also checked the "remote-disconnect-supervision". It
>consisted of approximately a one-second open loop (no current whatsoever)
>about five-to-seven seconds after the remote party hung up. (I'd suspect
>this is also central office equipment dependent and probably varies some
>between different types of offices.)

>Isn't trivia fun. ;)



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