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PBX Integration CSU/DSU???

I am connecting a 1751 to a Definity G3. On the PBX side I do not have a CSU/DSU. On the router side I have a MFT-T1 card which obviously has a built in CSU/DSU. I have done a few integrations to a Definity and each time I have had a CSU/DSU on the PBX side. When I do a "debug isdn q912" I see my SABME TX transmits and on the RX side I get "BAD FRAMES". My opinion is that the missing CSU/DSU is causing my problem. A few people I have talked to told me it was a clocking issue (this G3 cannot provide clocking so I have configured the router to do the clocking) and not a CSU/DSU issue. It is my understanding that if you have a CSU/DSU on one side you need it on the other side. If anyone has any thoughts please comment.


New Member

Re: PBX Integration CSU/DSU???

As I understand it, and I could be wrong, the CSU/DSU converts the signal from serial to 1-pair TDM. Essentially, if the port on the Definity is RJ-45, then you will not need a CSU/DSU, because RJ-45 will not support a serial connection. The "BAD FRAMES" could well indicate a clocking issue, or a linecode/framing config mismatch. Unfortunately, without a CSU/DSU you don't get the nice color-coded alarms. I have connected a voice gateway with a G3 (in my case it was a AS5300 gateway) and other than the PRI card, no special hardware was needed on the G3 side.


Re: PBX Integration CSU/DSU???

Thanks for the reply. It turns out the the 5ess switchtype does not support the Cisco Gateway being the Network Side (isdn protocol emulate network) I had to change to primary-ni on both sides and have the Gateway be the network side. Once I did that I got multiple frames established and everything came up on both sides. I am still having a little trouble. If I have debug isdn q931 and I make a call I do not see the q931 messages (even if I do a csim start number which rules out CallManager issues) I do not see the q931 messages. I have never configured a router to be the Network side so I am not sure if the q931 messages are different. All I see are some status_enq messages every now and again. Any ideas.

New Member

Re: PBX Integration CSU/DSU???

this can and does work send me an e-mail and I will send you a config for both sides.


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