Overview of switching systems, Electronic switching and stored program control systems, Centralized SPC, Availability, Distributed SPC, Enhanced services, Digital switching: time switching, space switching, time and space switches, Switching techniques: Circuit Switching, Message and Packet Switching. Traffic engineering: Traffic pattern, Grade of Service and blocking probability, modeling of switching systems: Markov Process, Birth-Death Process. Telephone network organization: Network management, Network services, various networking plans, types of networks, Routing plan, International numbering plan, National numbering plan, Numbering plan in India, Signaling: in channel signaling, common channel signaling.