Having had to remove Kazaa several times for its malware causing problems, finding out the founders of Skype were from Kazaa put me off.
--
Paul Carpenter | paul@pcserviceselectronics.co.uk
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Calm down. Learn the reasons why, learn about what ethernet is, its history, etc.
Model A come without ethernet. One of those is what you are looking for.
PS Troll alrm bell is ringing here.
SIP-to-SIP are are possible without touching PSTN or using PSTN phone numbers, they're not very common yet, but with IPV6 releiving NAT problems they are likely to become more common in the future,
-- For a good time: install ntp
this sort of thing?
not a balun:
this one is:
it converts unbalanced coaxial video signals to balnaced twisted pair and back
-- For a good time: install ntp
I do SIP-SIP trunks without the PSTN quite regularly, although my use case isn't typical. I use them to connect together geographically separated electromechanical phone exchanges.
See the youtube description to identify where the SIP trunks come in.
It's pointless, doesn't use an RPi (still haven't cracked the whole line interface FXO/FXS thing on the pi yet) but it does make a lovely noise.
-Paul
-- http://paulseward.com
Looked like that but as I said, the techies called them baluns.
-- Regards Dave Saville
Techs often call things what the look like or remind them of, not what they actually are.
-- -michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon
No those are not baluns, But then phone lines from a PABX are not balanced either.
-- Ineptocracy (in-ep-toc?-ra-cy) ? a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.
Would you care to explain why you make such an assertion?
-- Regards, J B Good
which part?
-- Ineptocracy (in-ep-toc?-ra-cy) ? a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.
====snip====
This bit:
"But then phone lines from a PABX are not balanced either."
-- Regards, J B Good
Yes, they are. The POTS invention of mr Bell was to modulate current, not voltage. This requires a balanced set of lines, but with a DC bias. Yes, there are inbalances when ringing, that is correct.
But otherwise the lines are well balanced. This applies to the proprietary interfaces of Nortel and Siemens too. The U interface of the ISDN BRI, and the G.703/G.704 interfaces even go to great lengths in the standards to assure that there are _exactly_ as many zeros and ones on the physical interface so there are no net galvanic currents on the balanced loop. The T1 also goes to great lengths towards this, but accepts some exceptions; always with more 1s than zeros.
I am not sure about how balanced other proprietary PABXes are, I have my doubts about the cheap Panasonic ones.
-- mrr
well they are not, in general. Why would they be?
All referenced to earth. No reason not to be.
sticking an audio transformer and a floating ring signal would be pretty pointless .
-- Ineptocracy (in-ep-toc?-ra-cy) ? a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.
Ah, I now see where the confusion arises now that you've explained what it was you were refering to.
A line doesn't need to be floating in order to be 'balanced'. In fact there are a few reasons why it can be "A Bad Thing"(tm) to have floating lines (balanced or not).
Although, out of necessity, one leg is connected via a high impedance inductor (normally a relay winding) to the positively earthed exchange battery terminal (normally referred to as the "A Leg" and the other leg has its connection to the negative terminal of the same exchange battery, also via another high impedance inductor (normally the other winding of the same relay) which is normally referred to as the "B Leg", as far as the voice signals (300Hz to 3.4KHz) are concerned, the line is still a balanced circuit.
It matters not that a 50v DC bias[1] is applied across the A and B legs to power the microphone circuit (transmitter) of the telephone from a central battery, the line still remains balanced for the purpose of eliminating crosstalk with other telephone circuits in the trunk cabling and external but adjacent sources of electrical noise.
[1] 50v is the traditional central battery voltage for main exchanges and larger PABXes but smaller PABX equipment can use lower voltages, typically 24v where long line length working isn't mandated in the specification.-- Regards, J B Good
to prevent crosstalk
you can do balanced without a transformer.
-- For a good time: install ntp
In PABX wiring? you are nuts!
unless you do an H bridge - and there is no point to that. .
-- Ineptocracy (in-ep-toc?-ra-cy) ? a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.
As one of an older generation, I well remember looking out of the window on long train journeys and watching as pairs of the lineside phone wires swapped places. Apparently this wasn't sloppy wiring, but a different ploy to reduce crosstalk in the long parallel circuits.
Now of course twisted pairs achieve the same thing, since the crosstalk induced at one half of the twist is cancelled by the crosstalk induced in the other half of the twist.
-- Alan Adams, from Northamptonshire alan@adamshome.org.uk http://www.nckc.org.uk/
Since it is only balanced for AC in the audio range, an inverter is enough to drive the pair balanced.
-- -michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon
That statement alone indicates that your nom de plume isn't an accurate attribution of your nature.
Anyone with the slightest knowledge of the theory of transmission lines would not have made such an outrageous statement. Worse still, a "Natural Philosopher" (the old name for a Scientist) would have at least checked their facts and saved themselves the embarassment of making such a retort.
Before you respond I think you aught, at least, do some basic research (wikipedia is a useful resource - hint, "Balanced Line" makes a good jumping off point into the subject).
-- Regards, J B Good
I am sure you simply dont know what you are talking about.
Inverter? wrong tool wrong job.
-- Ineptocracy (in-ep-toc?-ra-cy) ? a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.
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