The rapid expansion of the field of telecommunication networks call for a textbook in the area of telecommunication switching systems and. Telecommunication Switching Systems and Networks. Front Cover Why the hell you keep this book when you've restricted to 2 units only. What is the use of. The book gives a detailed discussion on topics such as fibre optic communication systems and networks, time division switching systems, data.
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It fulfils the need for a suitable textbook in the area of telecommunication switching systems and networks. The text covers, in a single volume, both switching. No part of the book be reproduced in any form, by Icograph or any . a treatment on both switching systems and telecommunication networks in a. terney.info - download Telecommunication Switching Systems and Networks book online at best prices in India on terney.info Read Telecommunication Switching .
A distinguishing feature of the text is the comprehensive coverage of all aspects of telecommunication engineering. The book should therefore prove to be an invaluable asset to both practising telecommunication professionals and students. Contents Foreword. Strowger Switching Systems.
Crossbar Switching. Electronic Space Division Switching. Speech Digitisation and Transmission. Time Division Switching. Optical Fibre Systems. Traffic Engineering. What are the differences between common control and direct control?
Common Control Direct Control Control subsystems are outside of switching system Control subsystems are integral part of switching system Ex.
Strowger exchange Ex. Stored program control Hard wired control subsystems Computer or processor control susbsystems Limited capability High capability Impossible to add new features Easy to add new features by changing control program 3. List 6 events that may occur in a telephone system and the corresponding actions to be taken by the common control system. Ans: The six events are: 1. Event sensing 3. Register finding 4.
Choosing appropriate register 5. Initial translator 6. Final translator The occurrence of events is signaled by operating relay which initiate control action. Line units handle the call request and call release signals. These line units themselves may initiate control actions on the occurrence of certain line events.
When a subscriber goes off hook, the event is sensed; the calling location is determined and marked for dial tone. The register finder is activated to seize a free register. Identity of the calling line is used to determine line category and the class of service to which the subscriber belongs.
A register appropriate to the line category is chosen, which then sends out the dial tone to the subscriber, in readiness to receive the dialing information. As soon as the initial digits usually are received in the register, they are passed on to the initial translator for processing.
The initial translator determines the route for the call through the network and decides whether a call should be put through or not. It also determines the charging method and the rates applicable to the subscriber. Such decisions are based on the class of service information of the subscriber which specifies details such as the following: Call barring, Call priority, Call charging, Origin based routing, No dialing calls 6.
If a call is destined to number in an exchange other than the present one processing the digits, the initial translator generates the required routing digits and passes them on to the register sender. Register sender uses appropriate signaling technique, depending on the requirements of the destination exchange.
If a call is destined to a subscriber within the same exchange, the digits are processed by the final translator. Calculate the time taken to dial a digit number in a DTMF telephone when a The exchange is capable of receiving a DTMF signals; and b The exchange can receive only pulse dialing Compare the result with a rotary telephone dialing.
How does the DTMF dial design take this into account? Ans: The probability of talk-off can be reduced by increasing the duration of the test applied to a signal by the receiver before accepting the signal as valid.
But, it is clearly unacceptable to expect the user to extend the push button operation for this purpose, beyond an interval that is natural to his dialing habit. A minimum of 40 ms has been chosen for both signal and inter-signal intervals, allowing for a dialing rate of over 10 signals per second.
Show that the harmonic frequencies of any two adjacent base frequencies in DTMF telephone cannot match within the 15 harmonics. Ans: Having decided on the frequency band and the spacing, the specific values of the frequencies can be so chosen as to avoid simple harmonic relationships like and between two adjacent frequencies in the same band and between pairs of frequencies in the two different bands, respectively. The adjacent frequencies in the same band have fixed ratio of , i.
Across the bands, the frequencies that lie along the diagonals have the ratio of Thus the chosen frequency values are such that they almost eliminate talk-off possibility due to harmonics.
If the transmitted power of the low band frequency signal from a DTMF telephone is 1 mW, what should be the power in mW of the high band frequencies? A telephone exchange supporting subscribers uses a DTMF dialing and a common control subsystem with digit receivers. Each digit receiver is assigned for duration of 5 seconds per subscriber call processing. A diagonal cross point matrix exchange supports users. On an average calls are put through everyday.
If the cross point contacts have a mean life of breaks and makes, estimate as to how often a cross point may be replaced in this exchange. Estimate the number of cross points required to design an exchange that supports users on a non-blocking basis and 50 transit, outgoing or incoming calls simultaneously.
A blocking crossbar switch is to be designed to support subscribers.
Electronic Space Division Switching 1. Define each of the following terms: Program, Procedure, processor, process, user, task, job and subroutine. Ans: Program: A program is a set of instructions executed in a predefined order and execution is dependent on the conditions in the program. Procedure: It is a part of the code written in a larger program which performs a specific task and is relatively independent of the remaining code.
Processor: The part of a computer system that interprets the instruction. Process: A process is an active entity. It can be thought of as a program under execution. User: A user is a person or a system that uses the system to perform some operation to get the results.
Task: A task is an execution pattern through address space or a set of processes that are loaded in memory. Job: Job is a single instance of a program. Subroutine: A section of code that implements a task, while it may be used at more than one point in a program. Blocked processes list is not maintained in priority order. In a switching system running thousands of processes, it cannot be easily determined that a process is in infinite loop.
What safeguards can be built into the operating system to prevent processes running indefinitely? Ans: To prevent processes running indefinitely or getting into deadlock following safeguards can be built into operating system. Mutual Exclusion - Must hold for non-sharable resources - When one process is using the resources the other processes should wait b.
No Preemption rights to download - If a process is requesting for a resource not available immediately then it should release all the resources it usually holds - Process will restart after it gets all of the resources d.
Circuit Wait - Improve vulnerability on all the resources - Process must request all the resources in increasing order of enumeration 4. Show that if P and V operations are not executed atomically indivisibly , the mutual exclusion may be violated. Ans: Consider that P and V are write operations.
Both P and V are making use of a same file. First P locks the file and writes to it and modifies the file, then V wants to read the original file, but it has been modified by the P modifier and this modification of file is not known to V. It reads the modified file and its results or outcomes are wrong. After that V modifies the file and then P reads the file and its results are also wrong. This situation is called violation of mutual exclusion. P V File 5. Show that a general semaphore can be implemented using binary semaphores.
Deadlock may occur in a road traffic junction. Illustrate with the help of a diagram. J1 J2 V1 V2 At the junction J1, vehicle V1 is blocking the vehicles that are going towards top direction at the same time at junction J2, vehicle V2 is blocking vehicles that are going towards right or down.
The same way other two junctions are also blocked be vehicles V3 and V4 at junction J3 and J4. No in this situation none of the vehicles have a chance to move either ways, thus deadlock occurs.
Semaphore waiting lists are usually implemented in FIFO order. What problems do you foresee if they are implemented in LIFO order? Ans: As the name indicates the processes that are last, will be removed from the list first. Processes that are entered first will be removed last. As P1 comes first, it is inserted into the stack. Similarly P2, P3, P4 are pushed into the stack as they come. The stack becomes full. At some time P4 gets channel to enter the semaphore and it removed from stack.
Next P5 and P6 enter into the stack. P2, P1 remain in the stack.
Next P6 enters the semaphore.