[Fwd: Re: [Asterisk-Users] Debugging zaphfc + PBX integration]

[Tim Robinson]

Gavin
What you said below does not quite make sense....

To connect your legacy PBX to a BT ISDN line your pbx would be running
in TE mode (Terminal) and the BT line runs in NT mode.

You would use a straight through Cat5 cable in this case.

In order to get your legacy PBX to talk to Asterisk, you need to put
your HFC card into NT mode, but I think you already undertstand this bit.

The mystery is in the cableing. the card is normally designed to run in
TE mode, and consequently the hardware does not swap over the TX and RX
pairs automatically when the software puts the card into NT mode.

Thus you need a crossover cable now that goes from your legacy PBX to
the HFC card.  This crossover cable needs to have the TX pins on your
legacy pbx (pins 4 and 5) connected to the RX pins of the HFC card (pins
3 and 6) and of course the other way around as well!)

In addition, you will almost certainly (unless your PBX has a DIP switch
or jumpers to add in terminating resistors) need to instert a 100 ohm
resistor between pins 3 and 6 as well as between pins 4 and 5.

I hope this is what your intentions are...!  If you want any more advice
do contact me off-list!

Rgds
Tim

Gavin Hamill wrote:
> On Saturday 16 April 2005 09:33, Tim Robinson wrote:
> 
> 
>>So I do not believe power is the issue...I strongly suspect you need the
>>100 ohm terminators and you need to check that your ISDN BRI crossover
>>cable is wired correctly.  i.e. the RX pins on one RJ45 connect to the
>>TX pins of the other.  Have a look at
> 
> 
> Tim that's just what I wanted to hear :) I'd rather do a dodgy 'wrapping CAT5 
> strands around resistors' effort than mess about with powered NT1s :))
> 
> I know the cables themselves are wired correctly because our local PBX support 
> made them, and they work perfectly when plugged into a real BT ISDN2e wallbox 
> =)
> 
> So, I'll pop down to Maplin on Monday and find myself some resistance :)
> 
> Cheers,
> Gavin.
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