Digital telephone systems Computer networks 12 Internet telephony 11 TCP/IP (Computer network protocol) 9 Data transmission systems 7 Automation 4 Digital communications 4 Frame relay (Data transmission) 4 Telecommunication 4 Telecommunication systems 4 Telephone systems 3 Asynchronous transfer mode 2 Internetworking (Telecommunication) 2 Modulation (Electronics) 2 Planning 2 Standards 2 Telephone switching systems, Electronic 2 Encyclopedias 1 Mobile communication systems 1 Modems 1 Reliability 1 Systems analysis 1 Telephone switching systems electronic 1 reliability 1