Posted: Tue May 26, 2009 3:26 pm Post subject: [asterisk-users] Maximum cable length for analog phone from
You are correct.
Telcos normally supply dial tone to business and residence for miles if
there is no DSL
Loading coils are used to offset the capacitance of cables, and precise
spacing of these is required, and are engineered for different types of
cable.
John Novack
David Gibbons wrote:
Quote:
I could be wrong but I don't think the cat5 limit of 100 meters
applies to any analog signaling over that copper. I believe it only
applies to Ethernet signaling.
-Dave
*From:* asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] *On Behalf Of *Danny
Nicholas
*Sent:* Tuesday, May 26, 2009 10:41 AM
*To:* baldvin@rogg.is; 'Asterisk Users Mailing List - Non-Commercial
Discussion'
*Subject:* Re: [asterisk-users] Maximum cable length for analog phone
from FXS port
The best a native cat5 can run is 100 meters. Unless you like paying
your telco huge bucks, you should go for some kind of SIP connection
to your box.
*From:* asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] *On Behalf Of
*asterisk-users@rogg.is
*Sent:* Tuesday, May 26, 2009 9:09 AM
*To:* 'Asterisk Users Mailing List - Non-Commercial Discussion'
*Subject:* [asterisk-users] Maximum cable length for analog phone from
FXS port
Hello.
I am looking for details of the maximum allowed/usable/effective
wire/cable length of the connection from a FXS port of Digium analog
cards to the analog telephone handset.
To clarify my intention, I need to have an analog telephone connection
to my asterisk box that is 3000 meters (3km) away at least. If you
have any details of ATA boxes or other similar devices that I could
use to do this, I'd appreciate your input. It must be able to use a
regular analog telephone handset on the far end.
I've searched high and low and either I'm not clever enough in using
the right terms for this or it is rarely documented?
Posted: Tue May 26, 2009 3:44 pm Post subject: [asterisk-users] Maximum cable length for analog phone from
You are exactly right. Cat 5 had no advantage over cheaper wire for voice, and the length limitations are meaningless. Consider that Cat 5 is typically use with signals that extent to 30 MHz or beyond. A voice grade analog circuit must go to 4 KHz (1/10,000 as much). At 4 KHz, the wire generally doesn’t even act like a controlled impedance.
Wilton
From:asterisk-users-bounces@lists.digium.com [mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of David Gibbons
Sent: Tuesday, May 26, 2009 8:50 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] Maximum cable length for analog phone from FXS port
I could be wrong but I don’t think the cat5 limit of 100 meters applies to any analog signaling over that copper. I believe it only applies to Ethernet signaling.
Posted: Tue May 26, 2009 3:49 pm Post subject: [asterisk-users] Maximum cable length for analog phone from
Wilton Helm wrote:
one thing I missed mentioning about fxs devices - the linksys/sipura
ones actually allow you to set line characteristics on the slic inside
it. you can vary from the 600ohm default, and tweak gains a bit. Some
mix of a capacitive line or different resistance may help. never tried
myself but there are a ton of things you can play with.
Quote:
There are a lot of factors that impact this. First, CAT 5, while
usable is overkill. Cat 3 (otherwise known as I/O wire) works equally
well for voice grade lines. That being said, for that long a run, a
heavier gauge wire would be better. I believe telcos use 18 – 22 guage
(Cat 5 and Cat 3 are both 26 awg). This has less resistive loss.
Most FXS or ATA devices use 24 volts or less for “battery”. That works
fine for short loops, but limits the range. A central office POTS port
normally uses 48 VDC which works well to several KM. If the customer
is at the end of a long run in a rural area, they use a “long line”
card which uses 75 volts. (In rural communities, they often place the
line cards in a roadside “remote terminal” and use statistically
multiplexed T1s to make it appear to the switch as a part of it.
That addresses the DC characteristics, which can be reduced to ohms
law. A phone needs around 8 V @ .02 A. The wire resistance determine
the drop (E = IR) and the source voltage determines whether there will
be enough left. The A.C. characteristics are more complicated. The FXS
must do a 2 wire to 4 wire conversion, which involves matching the
impedance of the line. The FXS is generally designed for relatively
short lines, so might not be able to match either the resistance or
capacitance found in a long run. Heavier wire will minimize this. In
addition to that, the transmit side of the 2 wire to 4 wire circuit
must be able to drive the load it sees, and again it may not be
designed with a long run in mind. Finally, COs line cards have the
ability to adjust receive and transmit gain to compensate for sound
level losses in long lines. While this isn’t routinely done on simple
circuits, it is an option an FXS doesn’t generally have. In addition,
the more gain that is inserted, the harder it is to balance to 2 wire
to 4 wire circuit, and the more complex it has to be in order to
support this.
Posted: Tue May 26, 2009 3:58 pm Post subject: [asterisk-users] Maximum cable length for analog phone from
On Tue, May 26, 2009 at 12:44:26PM -0400, Jon Pounder wrote:
Quote:
Wilton Helm wrote:
one thing I missed mentioning about fxs devices - the linksys/sipura
ones actually allow you to set line characteristics on the slic inside
it. you can vary from the 600ohm default, and tweak gains a bit. Some
mix of a capacitive line or different resistance may help. never tried
myself but there are a ton of things you can play with.
Posted: Tue May 26, 2009 6:47 pm Post subject: [asterisk-users] Maximum cable length for analog phone from
On Tue, 2009-05-26 at 10:26 -0400, John Novack wrote:
Quote:
That is a pretty long run.
The type of analog phone can be an issue. How LITTLE loop current will
it operate on? Most need more than 20 Ma to signal properly, and the
voltage output of the ATA needs to be known
Type of signaling? DTMF? pulse?
Interconnection cable wire size and capacitance will affect high
frequency response, loop current, inductive pickup and pulse shaping
to name just a few. The ATA requirements need to be known. A total
loop resistance of 500 ohms should work, but go out to 1200 and most
will fail
Do you really have control over this or will you be renting a pair
from the local telco?
Protection should be applied on both ends for safety of the user(s)
and devices.
There MUST be a better way???
Posted: Tue May 26, 2009 8:34 pm Post subject: [asterisk-users] Maximum cable length for analog phone from
Appreciate all your input folks. Much of it very helpful in the greater
context of the initial question.
Thank you for the suggestion of using various wireless devices, but I'm
stuck with fixed wiring since this is a security/emergency phone(s)
installation underground in large tunnels.
Also, switching to VOIP is not really the answer here because then I'm
forced to solve a lot of power, repeaters/switches problems that arise. So
I'm actually worse of than using the analog connections I think.
I do have some control over the wiring/cable chosen for this project but
still forced to find a solution where I can feed the analog "phone line" the
total 3km line distance.
I would love to find a way to do this in the Asterisk context with some sort
of FXS feed, either from Digium (or compatible) hardware or any of the
available ATA boxes. The Sapura box suggestion may be something and I'll
look closer into that as well as continuing to look for other ways to do
this.
tnx!
Baldvin
Quote:
-----Original Message-----
From: asterisk-users-bounces@lists.digium.com [mailto:asterisk-users-
bounces@lists.digium.com] On Behalf Of Hans Witvliet
Sent: 26. maí 2009 19:42
To: novackster@gmail.com; Asterisk Users Mailing List - Non-Commercial
Discussion
Subject: Re: [asterisk-users] Maximum cable length for analog phone
from FXS port
I would suggest making a wifi connection with directional hi-gain
antenna's.
Ans a small box at the other end. Have a look at:
http://www.fit-pc.net/fitpc-2-p-2.html or http://www.fit-
pc.info/downloads/handleidingen/fit_pc_2_eng.pdf
_______________________________________________
-- Bandwidth and Colocation Provided by http://www.api-digital.com --
Posted: Wed May 27, 2009 5:52 am Post subject: [asterisk-users] Maximum cable length for analog phone from
On Tue, May 26, 2009 at 07:52:53PM +0300, Tzafrir Cohen wrote:
Quote:
On Tue, May 26, 2009 at 12:44:26PM -0400, Jon Pounder wrote:
> Wilton Helm wrote:
>
> one thing I missed mentioning about fxs devices - the linksys/sipura
> ones actually allow you to set line characteristics on the slic inside
> it. you can vary from the 600ohm default, and tweak gains a bit. Some
> mix of a capacitive line or different resistance may help. never tried
> myself but there are a ton of things you can play with.
Any of those are actually important?
For the sake of completeness: try:
/sbin/modinfo wctdm
or:
/sbin/modinfo wctdm24xxp
You'll see quite a few parameters, many of which are essentially SLIC
(or DAA, for the FXO port) tweaks.
I suppose that if it were useful, there were already some demand to make
it tweakable (safely. Merely writing an arbitrary value to some register
at some point may or may not be wise). Hence my question.
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