Question 1: What is the primary purpose of a switching system in telecommunication networks?
Correct answer: b) Establishing connections between subscribers
Explanation: The fundamental purpose of any switching system is to establish connections between subscribers on demand, allowing communication to occur.
Question 2: Which of the following switching techniques establishes a dedicated physical path for the entire duration of a call?
Correct answer: c) Circuit switching
Explanation: Circuit switching establishes a dedicated communication path between two stations for the duration of the connection, which is characteristic of traditional telephone networks.
Question 3: In a step-by-step (SxS) switching system, what component directly responds to dial pulses?
Correct answer: d) Stepping switch
Explanation: In step-by-step systems, stepping switches (or Strowger switches) directly respond to dial pulses, moving step by step to establish the connection.
Question 4: What is the main advantage of crossbar switching over step-by-step switching?
Correct answer: c) Common control allowing more flexible routing
Explanation: Crossbar switches use common control systems that separate the control function from the switching matrix, allowing more flexible and efficient call routing.
Question 5: In telephony, what does the term "subscriber loop" refer to?
Correct answer: b) The connection between a subscriber and the local exchange
Explanation: The subscriber loop is the physical pair of wires connecting a telephone subscriber's equipment to the serving central office.
Question 6: Which signaling system uses separate frequencies outside the voice band for control signals?
Correct answer: c) Out-of-band signaling
Explanation: Out-of-band signaling uses frequencies outside the normal voice band (300-3400 Hz) for control signals, preventing interference with voice transmission.
Question 7: What is the primary function of a concentrator in a telephone exchange?
Correct answer: c) To reduce the number of trunks needed by sharing them among many subscribers
Explanation: Concentrators reduce costs by allowing many subscribers to share a smaller number of trunks, based on the statistical fact that not all subscribers need simultaneous connections.
Question 8: Which component in a telephone system provides the DC power needed for operation?
Correct answer: b) Central office battery
Explanation: The central office battery (typically -48V DC) provides operating power for telephones and signaling over the subscriber loop.
Question 9: In a crossbar switch, what is the function of the horizontal and vertical bars?
Correct answer: b) To select and connect specific input and output lines
Explanation: The horizontal bars select the input line, and the vertical bars select the output line. Their intersection point creates the connection.
Question 10: What is the main limitation of space-division switching compared to time-division switching?
Correct answer: d) All of the above
Explanation: Space-division switching requires a physical path for each connection, leading to higher cost per connection, limited scalability, and physical size constraints as the system grows.