Jawaharlal Nehru Technological University Hyderabad B.Tech III TELECOMMUNICATION SWITCHING SYSTEMS AND NETWORKS Previous Question Paper (May - 2019 - R15)

Switching systems are primarily classified into two main categories based on the technology used to establish connections:

1. Manual Switching System: Connections are established manually by a human operator using patch cords or plugs at a switchboard.
2. Automatic Switching System: Connections are established automatically without human intervention. This category is further divided into:
   • Electromechanical Switching: Utilizes mechanical movement of electrical contacts (e.g., Strowger or Crossbar systems).
   • Electronic Switching: Utilizes electronic components and stored program control (SPC), which can be further classified as Space Division Switching or Time Division Switching.

Traffic measurement is essential for network dimensioning and performance monitoring. It is primarily quantified using the following methods:

• Continuous Scanning: The state of all trunks or circuits is monitored continuously. The total traffic (A) in Erlangs is calculated by integrating the number of busy circuits over a specific observation period (T) and dividing by that period:
  A = (1/T) ∫ n(t) dt
  where n(t) is the number of busy circuits at time t.
• Periodic Scanning: The system samples the number of busy circuits at fixed, regular intervals. The average traffic is estimated by calculating the arithmetic mean of these samples over the observation period.
• Peg Counts and Holding Time: Traffic is also measured by counting the number of call attempts (peg count) and multiplying by the average holding time per call, then dividing by the total observation duration.