[cisco-voip] T1 xover or straight through?

[Tim Smith]

IAD would still be considered customer equipment as well I'd think.

Cheers,

Tim

On Wed, Jun 3, 2009 at 11:06 PM, Voice Noob <voicenoob at gmail.com> wrote:

>  I have had providers install an IAD device where they take the circuit
> from the Telco into their IAD. Then they hand of a PRI to my equipment from
> the IAD. In this case you need a Crossover T-1 cable.
>
>
>
> *From:* cisco-voip-bounces at puck.nether.net [mailto:
> cisco-voip-bounces at puck.nether.net] *On Behalf Of *Tim Smith
> *Sent:* Wednesday, June 03, 2009 7:37 AM
> *To:* Dane
> *Cc:* cisco-voip at puck.nether.net
> *Subject:* Re: [cisco-voip] T1 xover or straight through?
>
>
>
> Hi Dane..
>
> Simple rule for this.
>
> 1. Customer Equipment to Customer Equipment = T1/E1 cross over cable
> 2. Customer Equipment to Network = Straight through cable
>
> Customer Equipment = PBX, Voice cards on routers, key systems
> Network = the PSTN, your carrier, etc
>
> Bit more info to help explain hopefully :)
>
> Your 3845 T1 voice interface has pin outs as follows
>
> Pin
> 1 - Receive (RX) Ring
> 2 - RX Tip
> 4 - Transmit (TX) Ring
> 5 - TX Tip
>
> Think of receive as your ear and transmit as your mouth
> Straight through cables connect pin 1 to 1, 2 to 2, 4 to 4, 5 to 5.
>
> So when connecting customer to customer equipment with a straight through
> cable
> You are essentially connecting ear to ear and mouth to mouth.
> To get complete circuits you need ear to mouth and mouth to ear
>
> An E1/T1 cross over cable "crosses" the RX and TX connections as follows:
> Pin 1 to Pin 4
> Pin 2 to Pin 5
> Pin 4 to Pin 1
> Pin 5 to Pin 2
>
> Network / PSTN equipment has different pinouts.. i.e. it expects RX on
> pin's 1 and 2, and expects TX on Pins 4 and 5 from your equipment. Hence
> straight through cable required.
>
> Also dont forget if this is ISDN you also have a layer 2 network / user
> element to consider. i.e. if you connect 2 x customer equipment together -
> one side needs to be configured as Network side, and the other as user.
>
> Hope this helps a bit..
>
> Cheers,
>
> Tim
>
> On Wed, Jun 3, 2009 at 7:04 PM, Dane <dane at pktloss.net> wrote:
>
> First I wanted to say thanks for the replies and information.
>
> Second, well I got it sorted out finally.  I took down one of the
> PRI's after hours from the IAD and connected it to the 3845 with a
> straight through cable just to test.  It did not come up which is what
> I think I and everyone who responded on this list would have expected.
>  I connected the IAD to the 3845 with a T1 crossover just as I have
> the IAD connected to my CMM-6T1s and it came up.
>
> Now the kicker is that this same 3845 T1/PRI port connected to the
> AT&T demarc requires a straight through cable.
>
> I have to be honest and admit that this confuses me.  Of course its
> 4am and I have been busting my ass since 6am so I am not able to
> mentally sort this out.  Have to give it some thought when I have my
> wits how the 3845 port takes either a T1 crossover or a straight
> through depending on the other side apparently.
>
> Anyway, I thought it was interesting to note and share.
>
> Thanks again for the help.
>
>
>
>
>
> On Mon, Jun 1, 2009 at 12:31 PM, Go0se<me at go0se.com> wrote:
> > As a general rule a T1 crossover cable is always required between PBXs no
> > matter how you interconnect them. I'm not aware of a T1 controller that
> will
> > auto-mdix. You can build your own T1 crossover - cross pins 1&2 to pins
> 4&5.
> > (1 to 4 and 2 to 5)
> >
> > -Go0se
> > http://atc.go0se.com
> >
> > -----Original Message-----
> > From: cisco-voip-bounces at puck.nether.net
> > [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Dane
> > Sent: Monday, June 01, 2009 11:28 AM
> > To: cisco-voip at puck.nether.net
> > Subject: [cisco-voip] T1 xover or straight through?
> >
> > Anyone know if you need a straight through or t1 crossover to go from
> > an IAD to a 3845 with a PRI port?  We have some IAD's that terminate
> > with CMM's and those use t1 crossovers.  Not sure about the 3845
> > ports.
> >
> > Connecting to AT&T circuits to the 3845's required straight through.
> > Wish I had one to test.
> >
> > Just wondering if anyone might know, wondering if the 3845s can handle
> > either / or, and if the requirement comes from the demarc side (either
> > AT&T or IAD's).
> > _______________________________________________
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> >
> >
> >
> >
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