Bsnl Preparation Page 5

Ques-What are the types of lightning arrestors
(A) horn gap
(B) rod gap
(C) expulsion type
(D) all of the above

Ques-In a thyristor, ratio of latching current to holding current is
(A) 0.4
(B) 1.0
(C) 2.5
(D) None of these

Ques-The function of air conditioning system is

(A) Cooling and humidification            
(B) Cooling and dehumidification
(C) Heating and humidification            
(D) Heating and dehumidification

2. Communication : Modulation and demodulation – principles and operation of various types of AM,
FM and PM modulators/ demodulators; pulse modulation – TDM, PAM, PPM, PWM, Multiplexing, principles and applications of PCM.
Introduction of Basic block diagram of digital and data communication systems, coding error detection and correction techniques, Digital Modulation Techniques – ASK, ICW, FSK, PSK, Characteristics / working of data transmission circuits,
UART, USART, Modems, Protocols and their functions, brief idea of ISDN interfaces, local areas Network, Carrier Telephony – Features of carrier telephone system.Microwave Engineering : Microwave Devices, Wave – guides, Microwave Components, Microwave Antennas, Microwave Communication system- Block diagram & working principles of microwave communication link.

Sample Questions

Ques-Which of the following is not a transmission medium?
(A) telephone lines
(B)coaxial cables
(C) modem
(D) microwave systems

Ques-_____ is a digital process that allows several connections to share the high bandwidth of a link.
A)           FDM
B)           TDM
C)           WDM
D)           None of the above

Ques-Adding 1 and 1 in modulo-2 arithmetic results in _________.
(A)  1
(B)  2
(C)  0
(D)  None of the above

Ques-In case of open circuit transmission lines the reflection coefficient is
(A) 1
(B) 0.5
(C) -1
(D) Zero

3. Network, Filters and Transmission Lines : Two port network, Attenuators, Filters, Transmission Lines and their applications characteristic impedance of line, concept of reflection and standing waves on a transmission line, Transmission line equation, Principles of impedance matching Bandwidth consideration of a transmission line

Sample Questions

.Ques: Radiowaves of constant amplitude can be generated with
(a) FET
(b) filter
(c) rectifier
(d) oscillator
Ans is d

Ques: The current gain for a transistor working as common-base amplifier is 0.96. If the emitter current is 7.2 mA, then the base current is
(a)0.29mA
(b)0.35mA
(c)0.39 mA
(d) 0.43 mA
Ans is d

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