communication switching techniques - .communication switching techniques ... strowger switching


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    1. What is meant by telecommunication?

    Telecommunication network carry information signals among entities. Entities

    may be computers, a human being and data terminals. The process of information transfer

    may be file transfer, message transfer in between terminals, etc

    2. Define calling and called subscribers?

    Calling subscriber:

    In telephone conversation, the one who initiates the call

    Called subscriber:

    The one for whom the call.

    3. Define switching system?

    The subscribers are not connected directly with others; instead, they are connected

    to switching system. When a subscriber wants to communicate with another, a connection

    is establishing b/w the two switching system.

    Switching system also called as switching office (or) Exchange

    4. Define control function?

    The function performed by a Switching system in establishing and releasing


    5. What are the types of switching system?

    Manual Switching system

    Automatic Switching system

    6. What are the types of Automatic Switching system?

    Electromechanical switching system

    Electronic switching system

    7. What are the types of Electromechanical and Electronic switching system?

    Electromechanical: Electronic:

    Strowger switching Space division switching

    Crossbar switching Time division switching

    III YEAR/B.Tech-IT


    8. What is meant by Strowger switching?

    The control functions are performed by circuits associated with switching system

    9. What is meant by Electronic switching?

    The control functions are performed by the Processor (or) a Computer.

    It also called as Stored Program Control (SPC)

    10. Define Space division and Time division switching?

    Space division:

    A dedicated path is established b/w the calling and called subscriber for

    the entire duration of the call.

    Time division:

    The sampled values of speech signals are transmitted at fixed intervals.

    11. Define Trunk?

    The Links that run between switching system are called trunks

    12. Define Transducer?

    Transducers perform the energy conversion. whether optical signal to voice signals (or)

    Electrical signal to Voice signals

    13. What are the telecommunication networks?

    Telegraph networks

    Telex networks

    Telephone networks

    Data networks

    14. Basic components of switching system?

    Inlets, outlets and switching network

    15. Define symmetric network?

    Inlets and outlets are equal in a switching (N=M)

    16. Define blocking and non-blocking network?

    Blocking network:

    There is a path free in the network

    Non-blocking network:

    There is no path free in the network

    17. What is meant by Interdigit gap?

    Two successive trains are distinguished from one another by a pause in between


    18. What are the different types of signaling tones?

    Dial tone


    Ringing tone

    Busy tone

    Number unobtainable tone

    Routing tone

    19. What are the design parameters?

    Cost of the switching system

    Traffic handling capability

    Equipment utilization factor

    Cost capacity index

    20. What are the control functions in switching system?

    Event monitoring

    Call processing


    Operation and maintenance

    21. What are the service information are needed for rates of subscriber?

    Call barring

    Call priority

    Call charging

    Origin based routing

    No dialing calls

    22. What is the procedure for establishing a connection in crossbar switching?

    Energize horizontal bar Energize vertical bar

    Energize vertical bar (or) energize horizontal bar

    De-energize horizontal bar De-energize vertical bar

    23. What is the principle of crossbar switching?

    To provide a matrix oh n*m sets of contact with only n+m activators (or) less to

    select one of the n*m sets of contacts.




    1. Define stored program control?

    A program or a set of instruction to a computer is stored in its memory and

    executed automatically one by one by the processor.

    2. What are the electronic space division switching systems?

    Electromechanical switching

    Electronic switching

    3. What are two approaches to organizing stored program control?

    Centralized SPC

    Distributed SPC

    4. Define centralized SPC?

    All the control equipment is controlled by a single processor. It must be capable

    of processing 10-100 calls per second.

    5. What are the modes of dual processor?

    Standby mode

    Synchronous duplex mode

    Load sharing mode

    6. Define standby mode?

    One processor is active and the other is on standby, both hardware and software.

    It is used to determine which of the subscribers and trunks are busy (or) free.

    7. Define Synchronous duplex mode?

    The hardware coupling is provided between the two processors which execute the

    same set of instructions and compare the results continuously.

    8. Define availability and unavailability of the processor?

    A = MTBF/(MTBF + MTTR)

    A= availability

    MTBF=Mean time b/w failure

    MTTR=Mean time to repair


    U= unavailability

    9. What are the interrupts in SPC?

    Vectored interrupt

    Non-vectored interrupt


    10. Define Distributed SPC?

    The control functions are shared by many processors within the exchange itself.

    This offers better availability and reliability.

    11. Differance between micro programmed control and hard-wired control?

    Micro programmed control Hard-wired control

    1. Flexible not flexible

    2. Slower faster

    3. More expensive for processing functions less expensive

    4. Easier to implement complex processing functions difficult to implement

    12. Difference between single and multistage networks?

    i) Inlet to outlet is through a Inlet to outlet is through a

    Single cross point multiple cross point

    ii) Use of a single crosspoint per Use of a multiple crosspoint may

    Connection results in better quality link degrade the quality of a connection

    iii) Time for establishing a call is less time for establishing a call is


    iv) The network is none blocking the network is blocking

    13. Define full availability?

    There are k alternative paths for any inlets/outlets pair connection. The network is

    said to be full connectivity (or) full availability

    14. Define baseline networks?

    Networks that support N simultaneous connections but under restricted traffic

    distribution conditions

    15. When a network is called as analog and digital time division switching?

    When PAM samples are switched in a time division manner, the switch is called as

    analog time division switching.

    When PCM samples are switched in a time division manner, the switch is called as

    digital time division switching.

    16. Define time division space switching?

    A single switching element (bus) is being time shared by N connection, all of

    which can be active simultaneously and a physical connection is establishing b/w

    inlet and outlet duration of time sample transfer is called time division space


    17. What is the controlling in a time division time switching?

    Sequential write / random read


    Random write / Sequential read

    Random input / random output

    18. What are the two modes of time division time switching?

    Phased operation

    Slotted operation

    19. Define time multiplexed switch?

    The inlets and outlets are trunks which carry time division multiplexed data

    streams. Such a switches called a time multiplexed switch.

    20. Define combination switching?

    It can be built by using a number of stages of time and space switches according

    to time space (TS) and space time (ST).



    1. Why we are going for traffic engineering?

    The load (or) traffic pattern on the network varies during the day with heavy

    traffic at certain times and low traffic at other times. Such a bisis are provides a traffic


    2. What is meant by busy hour?

    In a day, the 60 minute interval in which the traffic is highest is called busy hour


    3. What are the basic busy hours?

    Busy hour

    Peak busy hour

    Time consistent busy hour

    4. Define busy hour calling rate and day-to-busy hour traffic ratio?

    Busy hour calling rate = average busy hour calls / total number of subscriber



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