Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

RJ45 cable for PRI?

Will a normal RJ45 from Cisco Gateway to Telco terminating device work for new PRI? Or is a RJ48 required?


  • IP Telephony
Hall of Fame Super Gold

Re: RJ45 cable for PRI?

Do not use ethernet cable. Please use only proper T1 cable, 100 Ohm impedence, with the correct pinout ans pair twisting, as per manual.

Hall of Fame Super Red

Re: RJ45 cable for PRI?

Hi Jerry,

Hope all is well :) Just wanted to add a note to the good info from my friend Paolo. This doc has some good references for the RJ48 Pinouts;

Hope this helps!


"May your heart always be joyful And may your song always be sung May you stay forever young " - Dylan

Re: RJ45 cable for PRI?

We use RJ45 for our PRIs without any Problems. If you just need a short Cable to connect to your E1, RJ45 would be fine.

New Member

Re: RJ45 cable for PRI?

Sometimes the telco terminating box will only accept the keyed RJ48C but in most cases we use RJ45 straight through with no problems.

Hall of Fame Super Gold

Re: RJ45 cable for PRI?

Rj48C twisting is different from ethernet, hence no protection from interference, and bigger radiated interfences.

All is good until strange eproblems happens, at that time you will replace the cable anyway, so why don't do things rights since the beginning.

New Member

Re: RJ45 cable for PRI?

Agreed, I'm all for doing things properly and if the telco kit does have the proper keyed socket you are safe.