Welcome Message

Hello my dear reader,

Welcome to my blog, which is dedicated to Cisco technologies. On its pages we will talk about the limitless world of telephony and networking.

We will focus mostly on Cisco collaboration solutions and technologies. These are IP PBX based on Cisco Unified Communications Manager and Cisco Unified Communications Manager Express, Cisco contact centers, Cisco Voice Gateways, etc. Also, I will introduce you the education news: Cisco authorized courses, my own developed training programs, our upcoming events, online learning.

If you have any questions regarding my posts, job or activities, please feel free to ask your questions. I will try to answer them when I have time.

If you are satisfied with the content of my blog, isn’t that worth a beer or coffee? Donations help me to continue supporting the blog and creating new posts here — things for which I spend hours of my free time! Thank you very much!

Sincerely, Dmytro Benda

Sunday, November 27, 2011

E1 Link Clocking on Cisco Voice Gateways - How to Avoid "Slips"

Good morning! :)

Recently, at one of the courses, my students asked me the question - how to get rid of such a phenomenon as "slips" on the E1 links when connecting a Cisco gateway to another PBX or to PSTN? I would like to suggest a solution for everyone who faced a similar problem.

What is a "slip"? This is the term used for one of the errors related to the wrong clocking  (desynchronization) of the E1 link. For the correct operation of the E1 stream, its exact clocking with the opposite side is necessary in order to know at what points in time the samples of certain timeslots are transmitted. If the clocking is wrong, the PBX can mistakenly take the sample bits of neighboring timeslots for the sample bits of this time slot, i.e., in other words, the PBX does not know at what point in time the sample bits of this timeslot are transmitted.