The Picturephone System: Transmission Plan
01 February 1971
The signal standards and performance objectives for the overall system discussed in previous papers 1,2 were arrived at through a series of subjective tests and system studies which indicated that the resultant picture quality would be acceptable to the user. Given the end-to-end transmission objectives, the intent in formulating a transmission plan for the network is to strike a balance between the cost and performance of each of the components: the station equipment, loops, local switching and trunking, and long-haul switching and trunking. Impairments are allocated to each of these components such that the overall cost of the service is minimized, taking into account that the loop connecting the station equipment to the local central office is normally dedicated to a single customer, whereas the switching equipment and trunks are shared by hundreds or perhaps thousands of customers.