[asterisk-users] Slightly OT:CSU on Digium cards, and it's requirement

[C F]

On 6/11/07, Jon Pounder <JonP at inline.net> wrote:
> Quoting C F <shmaltz at gmail.com>:
>
> > Do the Digium cards have a built in CSU?
> > Is a CSU an FCC requirement? or just a carrier requirement?
>
> if you expect things to work you need one regardless of regulations,
> yes the digium cards have it built in, as do most modern t1 cards.

I disagree with this, I have several T1s that don't use Digium
equipment and are directly connecting to T1 cards that DONT have a CSU
and work fine. The reason this thing came up was because I was going
thru documentation for such a card and it mentioned it's an FCC
requirement.

>
> if the "T1" terminates in something that looks like a scsi connector
> you have an hssi interface most likely, if it terminates in an rj45,
> especially if it has status lights, you most likely have yourself a
> csu built in, sometimes you'll have a db15 instead of the rj45
> depending on the country it was designed for but it still works the
> same if you just get a passive adapter to get to the connector type
> you need (or make one, t1 speed is a 1/8th of the slowest ethernet so
> construction technique is not too critical if you ever made an
> ethernet cable)
>
>
> coming in from the raw copper pair this is what needs to be there :
>
> telco supplied "pairgain" box which is normally an HDSL modem that
> gets you from a type of dsl circuit to a 2 pair T1 / DS1 circuit
> (don't confuse DSL and DS ONE in this sentence)
>
> that is the actual demarcation point.
>
> then comes your csu/(dsu)
> This is the point where remote loopback tests can be done without
> actually talking to the guts of your hardware, telco can normally do
> it to their box as well but when they do a line test they loop to your
> csu normally.
>
> next comes a serial interface of some sort, in a more modern setup its
> indivisible from the csu, in the old days you had a physical
> synchronous serial cable between running at t1 clock speed.
>
> Where its separate the serial port is also known as an hssi connection
> or high speed serial interface.
>
>
> So without the csu in the mix converting the t1 channel frame encoding
> down to the actual serial data, you have no way to talk to the channel.
>
> its like saying I have a usb port, do I really need the ethernet
> dongle in order to plug it into an ethernet jack ? Then again some
> hardware has an ethernet jack right on it, but it still has all the
> same ethernet hardware as the dongle in there somewhere even if there
> is no physical usb path between the pci bus and the ethernet, it still
> accomplishes the same thing.
>
> the csu is sort of like the part of the modem where the start and stop
> bits are added into the actual data before hitting the actual modem
> proper where the bits are converted to tones, we don't generally make
> the distinction on that part of the circuit since the rest is useless
> without it.
>

That specific T1/PRI card I'm talking about has an JR45 connector and
does not have a built in CSU. Which brings me back to the second part
of my original question, is it required by law.

Thank you


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> Jon Pounder
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