Description : Explain the basic architecture of digital switching systems. Explain in detail companding.
Last Answer : A simple N X N time division space switch is shown in Fig. The switch can be represented in an equivalence form as a two-stage network with N X 1 and 1 X N switching matrices for the first and ... = Parameter used to define the amount of compression Vout = Compressed output voltage.
Description : Show how finite state machine model helps in designing a switching system and give a typical example.
Last Answer : Switching system basically belongs to the class of finite state machines (FSM) which are asynchronous in nature and follows a sequential logic for their operation. They can be modeled by ... circuits and memory elements. Clocked synchronous operation shown in Fig. overcome such problems.
Description : MAC address helps in (A) multimedia access control. (B) media access control. (C) mobile access control. (D) master access point control
Last Answer : (B) media access control.
Description : Which of the following contributes to harmonics distortion in amplifiers? A) Positive feedback B) Presence of noise C) Defective active device D) Non linearity in active device.
Last Answer : D) Non linearity in active device.
Description : The Signalling connection control part (SCCP) and message transfer part (MTP) together are referred to as (A) Signal Switching Points (SSPs) (B) Signal Transfer Points (STPs) (C) Signal Control Points (SCPs) (D) Network service part (NSP)
Last Answer : (D) Network service part (NSP)
Description : ARQ is transmitted in the event of: (A) Loss of signal (B) Error in received data (C) Improve reliability (D) During time out
Last Answer : (B) Error in received data
Description : The analog signal needs to be sampled at a minimum sampling rate of: (A) 2fs (B) 1/(2fs) (C) fs/2 (D) 2/fs
Last Answer : (A) 2fs
Description : Call request signal is: (A) Seize signal (B) Idle state signal (C) Line identification signal (D) Called subscriber alert signal
Last Answer : (A) Seize signal
Description : Example of circuit switching and S&F (Stored and Forward) switching is (A) Telephone and Post of Telegraph (B) Video Signal Post or Telegraph (C) Digital Signal Post or Telegraph (D) None of above
Last Answer : (A) Telephone and Post of Telegraph
Description : As per Nyquist criterion the sampling rate is (A) 2fs (B) (1/2)fs (C) (1/2fs) (D) (2/fs) Where fs is the signal frequency
Description : An off-hook signal will repeat for a/an ________duration. (A) finite (B) infinite (C) duration of 40 seconds (D) duration of 80 seconds
Last Answer : (A) finite
Description : Echo suppressor is detrimental to full duplex operation because (A) It disables one of the two pairs in a four-wire trunk line when a signal is detected on the other pair. (B) It enables one of the ... It activates both the pairs of a four-wire trunk line. (D) It is independent of line conditions.
Last Answer : (A) It disables one of the two pairs in a four-wire trunk line when a signal is detected on the other pair.
Description : Which causes a quantization noise in PCM system? A. Serial transmission errors B. The approximation of the quantized signal C. The synchronization between encoder and decoder D. Binary coding techniques
Last Answer : B. The approximation of the quantized signal
Last Answer : The approximation of the quantized signal
Description : What is the quantization signal-to-noise ratio if an 8-bit PCM code is used? A. 40 dB B. 50 dB C. 60 dB D. 65 dB
Last Answer : B. 50 dB
Description : Quantization noise is caused by A. binary coding techniques B. serial transmission errors C. the synchronization between encoder and decoder D. the approximation of the quantized signal
Last Answer : D. the approximation of the quantized signal
Description : What is the reason why companding is employed in PCM systems? A. To overcome impulse noise in PCM receivers B. To allow amplitude limiting in the receivers C. To solve quantizing noise problem D. To protect small signals in PCM from quantizing distortion
Last Answer : D. To protect small signals in PCM from quantizing distortion
Description : Find the total number of link L having five entities? Explain differences between folded and non-folded network.
Last Answer : Folded network: When all the inlets/outlets are connected to the subscriber lines, the logical connection appears as shown in Fig. In this case, the output lines are folded back to the input ... non-folded network to be non-blocking, the network should support N simultaneous switching paths.
Description : A two stage non-blocking network requires twice the number of switching elements as the single stage non-blocking network. (A) TRUE (B) FALSE
Last Answer : Ans: (A)
Description : ECE Board Exam March 1996 The expander in a companding device provides ___________. A. greater amplification for low signal levels B. less amplification for low signal levels C. greater amplification for high signal levels D. lesser pressure for transmission
Last Answer : B. less amplification for low signal levels
Description : What causes image interference? A. Low gain B. High IF C. Poor front-end selectivity D. Low signal-to-noise ratio
Last Answer : C. Poor front-end selectivity
Description : What is the effect in over modulated amplitude modulated radio broadcasting transmission? A. Interference to adjacent channel B. Higher fidelity C. Increase noise D. Higher audio signal
Last Answer : A. Interference to adjacent channel
Description : The random and unpredictable electric signal from natural causes, both internal and external to the system is know as ________. A. Distortion B. Noise C. Attenuation D. Interference
Last Answer : B. Noise
Description : What do you mean by numbering and addressing? Draw the ISDN address structure and explain how the addressing works?
Last Answer : Numbering and Addressing: In telephone and data networks, the end equipments are more often single units than multiple devices units like PABX or LAN. Historically, a telephone, a computer, or a ... as reference point may also be addressed by using direct inward dialing (DID) feature.
Description : Explain the process of inter-register signalling.
Last Answer : Registers are used in common control exchanges to store and analyze routing data. They are provided on a common basis is a single register provides routing data for a number of speech circuits. Once a call ... it is released and the originating register signals to the next register.
Description : Draw a centralized SPC organization and explain how it works under load sharing operation.
Last Answer : In centralized control, all the control equipment is replaced by a single processor which must be quite powerful. It must be capable of processing 10 to 100 calls per second, depending on the ... both the processors are active simultaneously and share the load and the resources dynamically.
Description : Explain FDM and show how CCITT standards help in building the base band?
Last Answer : Frequency Division Multiplexing: It is the process of combining several information channels by shifting their signals to different frequency groups within the spectrum so that they can be transmitted simultaneously ... of 24 channels were assembled together in one stage of modulation.
Description : What are transmission bridges? How do they help in satisfying the connectivity?
Last Answer : A typical transmission bridge is shown in Fig. The series capacitance and the shunt inductances of the two relays provide a high-pass filter to transmit the AC speech signals, while the relays respond independently to the DC loop/disconnect signals from the calling and called customer.
Description : What are the different ways of designing 100 line exchange using uni selector and two motion selectors? Show at least three variations. Which is the best option?
Last Answer : Here three different designing methods for 100 line exchange are discussed: Design 1: Here, Strowger switching system is designed using one two-motion selector for each subscriber. A ... only under certain specific traffic conditions and generally lead to higher blocking probabilities.
Description : How numbering plan is achieved in modern telephony? Give the structure with example.
Last Answer : The objective of numbering plan is to uniquely identify every subscriber connected to a telecommunication network. A numbering plan may be open, semiopen or closed. An open-numbering plan permits wide ... known as the subscriber number which is the number listed in the telephone directory.
Description : How does a touch tone receiver differs from pulsed dial receiver? Explain with schematic.
Last Answer : Pulse dialing: 1. Generated through make and break contact. 2. DC Current pulse is generated. 3. Each number is separated by a short pause to prevent overlapping. 4. Codes ... dialing pulse is not misinterpreted as the phone being returned to its on-hook (idle) condition.
Description : Discuss different Routing plan adopted in a Telephone network.
Last Answer : Hierarchical networks are capable of handing heavy traffic where required, and at the same time use minimal number of trunk groups. Three methods are used for deciding on the route for a ... selection methods can be implemented. Computer based routing is a standard feature in data networks.
Description : Discuss briefly subscriber loop system. Give some technical specification for subscriber lines.
Last Answer : Subscriber Loop System: Every subscriber in a telephone network is connected generally to the nearest switching office by means of a dedicated pair of wires. Subscriber loop refers to this pair of wires. It is un ... 1. Diameter of wire 2. D.C. resistance per Km 3. Attenuation per Km
Description : What is Traffic Engineering? Define the term busy hour, traffic intensity and grade of service.
Last Answer : Traffic engineering provides the basis for analysis and design of telecommunication network to carry a given traffic at a particular loss probability. It provides a means to determine the quantum of common equipments ... A0 Where A= offered traffic A0 = carried traffic A-A0= lost traffic
Description : Explain topology method used in LAN technology in detail.
Last Answer : LAN Topologies: Network topology is a physical schematic which shows interconnection of the many users. There are four basic topologies as under: (i) Direct Connection or one to all topology ( ... temporarily, inserting the new node and then reestablishing the complete ring path.
Description : List all seven layer of OSI model and describe function of application layer.
Last Answer : The layers of OSI model are as follows: (1) The Physical Layer: This defines an interface in terms of the connections, voltage levels and data rate, in order for signals to ... with the applications programs needed. Examples include electronic mail, word processing, banking transactions, etc.
Description : Explain simple telephone communication system with circuit and equation of current flow in microphone?
Last Answer : Simple Telephone Communication: In the simplest form of a telephone circuit, there is one way communication involving two entities, one receiving (listening) and the other transmitting (talking). ... carrier wave in AM system. The quantity m is equivalent to the modulation index in AM.
Description : Explain crossbar exchange, with all call processing steps and diagrams
Last Answer : The basic idea of crossbar switching is to provide a matrix of n x m sets of contacts with only n + m activators or less to select one of the n x m sets of contacts. This form of ... a contact is established at the cross point 6 such that the subscriber B is connected to the subscriber C.
Description : What are the advantages and disadvantages of packet switching over circuit switching?
Last Answer : The comparison of packet switching and circuit switching showing advantages and disadvantages of packet switching over circuit switching is given below:
Description : What is a Modem? What is the need of MODEM in data communication? Explain at least one modulation technique used for high speed modems.
Last Answer : Modems are essentially used to interface digital circuits to transmit information on analogue channels like telephone systems. Modem (from modulator-demodulator) is a device that modulates an analogue carrier ... caused by the lines makes the detection even harder than amplitude modulation.
Description : What are the advantages of CCS over in-channel signalling?
Last Answer : The advantages of CCS over in-channel signalling are listed below: a. Information can be exchange between the processors much more rapidly than when channel associated signaling is used. b ... for functions other than call processing, for example for maintenance or network management purposes.
Description : Explain the CCITT hierarchical structure of switching and routing using block schematic.
Last Answer : Hierarchical network are capable of handing heavy traffic where required, and at the same time use minimal number of trunk groups. A 5-level switching hierarchy is recommended by CCITT as ... A strictly hierarchical network suffers from serious drawback i.e. its poor fault tolerance future.
Description : Through two block diagrams explain the difference between Space division and time division switching.
Last Answer : Space and Time Switching: Space Switches: Connections can be made between incoming and outgoing PCM highways by means of a cross point matrix of the form shown in Fig. However, different channels of ... of the speech store, whose contents are read out and sent over the outgoing highway.
Description : What are different control function categories, explain, how they help in signalling and control.
Last Answer : In some switching systems, the control subsystem may be an integral part of the switching network itself. Such system is known as direct control switching systems. Those systems in which the control ... may be carried out at the level of the common control unit or the switching network.
Description : Explain the architecture of SS7 and compare with seven-layer OSI architecture.
Last Answer : A block schematic diagram of the CCITT no. 7 signaling system is shown in fig. Signal messages are passed from the central processor of the sending exchange to the CCS system. This consists of the microprocessor based ... part (TUE), the data user part(DUP) and the (ISDN) user part (ISDN-UP).
Description : What is centralized SPC, what are its modes of operation; explain the working of any one of these?
Last Answer : In centralized control, all the control equipment is replaced by a single processor which must be quite powerful. It must be capable of processing 10 to 100 calls per second, depending on ... The shared secondary storage need not be duplicated and simple unit level redundancy would suffice.
Description : Compare electromechanical switching system with electronic switching system.
Last Answer : Ans:
Description : In a hundred-line exchange 24 two-motion selectors are used. Draw the schematic you suggest for this exchange and explain its working. How many simultaneous calls can be made during peak hour in this exchange?
Last Answer : The desired schematic for 100 lines exchange with 24 two motion selectors is shown in Fig. In the case, 24 simultaneous calls can be put through the switch . Typically, a 24- ... selector. At the next step, the two-motion selector responds to the dial pulses for appropriate connection.
Description : Explain the terms. (i) Register marker. (ii) Conditional selection.
Last Answer : (i) Register marker: Strowger selectors perform counting and searching. However, the crossbar switch has no intelligence'. Something external to the switch must decide which magnets to operate. This is ... are found to be free does it operate the switches. This is called Conditional Selection.
Description : Write short notes (i)Telephone hand set and it’s working. (ii) CPU based exchange
Last Answer : (i) A standard telephone set is comprised of a transmitter, a receiver, and electrical network for equalization, associated circuitry to control side tone levels and to regulate signal power, ... commands are designed to be of variable length necessitating the use of an end-of-command symbol