The Picturephone System: The 850A PBX

1.1 General For business people, person-to-person conversation is the most complete means of communicating; therefore, the first major users of Picturephone service are likely to be business persons. Switching systems such as a Private Branch Exchange (PBX), or a key telephone arrangement are an integral part of most business communications set-ups. To obtain full utilization of the existing telephone network, Picturephone service is to be added as an integral part of telephone service; therefore, Picturephone service must be added to these systems serving the business community.1 The 850A PBX has been designed to provide Picturephone service to customers served by 701B or 757A electromechanical PBXs. 1.2 Objectives The objective of the 850A PBX is to provide Picturephone service on 701B and 757A types of electromechanical PBXs, step-by-step (SXS) and crossbar (X-bar) respectively, with a common machine. In addition, the 850A PBX is to provide the same services on Picturephone service that the customer has on telephone; therefore, the 850A provides Picturephone service on all the Communications Service Packages, series 100, 200, 300 and centrex (CU) I and II. Flexibility of the 850A in working with either SXS or X-bar PBXs is achieved by using the 850A in parallel with the existing customer telephone switching system. In the 850A Picturephone telephone sys585