The Picturephone System: Key Telephone Systems

A key telephone system (KTS) is a customer-controlled switching system which permits use of a station set for. more than one Central Office, Private Branch Exchange (PBX) or intercom line by switching from one line to another. Generally speaking, customers can signal from one station to another, transfer calls between stations, hold a call on one line while talking on another, and converse between stations without making use of a Central Office (CO) or PBX line.1 Picturephone service adds a new dimension to key systems in that now video as well as audio switching must take place to connect one Picturephone station set to a number of Picturephone CO or PBX lines or intercoms. Five key system services will be offered for Picturephone service: 2 two Central Office or PBX line services, two intercom services and one add-on-conference service. The line services will permit (i) boss/ secretary access to one Picturephone CO or PBX line,* and (u) shared access of one line by a number of boss/secretary groups. The first of these services is referred to as single-group line service while the second is referred to as multigroup line service. The intercom services will consist of (i) a single-link Picturephone intercom that * Hereafter referred to as "Line." 567