61005563-Standard-Notes-Tsn-Unit-II.pdf

61005563-Standard-Notes-Tsn-Unit-II.pdf - 2...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
2 Telecommunication Switching and Networks ECE study materials [ ] Page 1 TIME DIVISION SWITCHING Space and time switching: A tandem switching centre or the route switch of a local exchange must be able to connect any channel on one of its incoming PCM highways to any channel of an outgoing PCM highway. The incoming and outgoing highways are spatially separate, so the connection requires space switching. A connection will occupy different time slots on the incoming and outgoing highways. Thus the switching network must be able to receive PCM samples from one time slot and re-transmit them in a different time slot. This is known as Time slot interchange or Time switching. Space switches: Crosspoint matrix connects incoming and outgoing PCM highways. Different channels of an incoming PCM frame may need to be switched by different crosspoints in order to reach different destinations.Crosspoint is a 2 input AND gate. One input is connected to incoming PCM highway and another to connection store that produces a pulse at required instants. Figure below shows space switches with k incoming, m outgoing PCM highways carrying n channels. The connection store for each column of crosspoints is a memory with an address location for each time slot which stores the number of the crosspoint to be operated in that time slot. This number is written into the address by the controlling processor in order to set up the connection. The numbers are read out cyclically in synchronism with incoming PCM frame. In each time slot, the number stored at corresponding store address is read out and decoding logic converts this into a pulse on a single lead to operate relevant crosspoint. Since a crosspoint can make a different connection in each of n time slots, it is equivalent to n crosspoints in a space division network. fig. Space switch
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 Telecommunication Switching and Networks ECE study materials [ ] Page 2 Time switches: Time switch connects an incoming n-channel PCM highway to an outgoing n- channel PCM highway. Since any incoming channel can be connected to any outgoing channel, it is equivalent to a space-division crosspoint matrix with n incoming and outgoing trunks. Time slot interchange is carried out by means of two stores, each having a storage address for every channel of the PCM frame. Speech store consists of data of each of the incoming time slots (i.e. its speech sample) at a corresponding address. Each address of the connection store corresponds to a time slot on outgoing highway. It contains number of time slot on incoming highway whose sample is to be re-transmitted in that outgoing time slot. Information is read into the speech store cyclically in synchronism with the incoming PCM system; however random access read out is used. The connection store has cyclic read out, but writing is non-cyclic.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern