Section 1: Introduction -- The future -- Machines that use data transmission -- Present-day systems using data transmission -- Section 2: The world's telecommunication links -- Organizations involved in telecommunications -- A summary of types of lines and tariffs -- Telegraphy -- DC signaling -- A.C. transmission media -- Attenuation and repeaters -- Frequency and bandwidth -- The maximum capacity of a channel -- Noise and distortion -- Modulation and demodulation -- Pulse techniques -- Multiplexing -- Trunks and wideband facilities -- Supervisory signals -- Exchanges and switching -- Computer controlled line switching -- Communication satellites -- Data errors -- The treatment of errors -- Line termination for data transmission -- Conversations with computers.