A new voice multiplexing system for subscriber carrier system called "envelope multiplexing" is proposed in this paper. In this scheme, transmission format is composed of a frame in which at most one signal from one subscriber appears. Time slots in a frame can be assigned on statistical multiplexing basis and if all the demand can not be satisfied in a frame, the excessive information will be lost. The design principle and the characteristics of the system are described in this paper.

This paper describes the systems aspect of the study which has been conducted to explore the realizability of an on-line library that is capable of providing on-line, to many remote users with original document information. The concept of an on-line library is presented first and then design considerations for a prototype system is described. The prototype system includes a bibliographic information retrieval subsystem, an original document information retrieval subsystem, and a remote terminal subsystem. The bibliographic information retrieval subsystem is capable of interactively retrieving a bibliographic database and a location information database which are stored in magnetic disks. The original document information retrieval subsystem is capable of selectively providing, in accordance with the result of bibliographic information retrieval, pages of original documents which are stored in a direct-read-after-write (DRAW) type optical disk. The remote terminal subsystem performs interactive bibliographic information retrieval and hard-copy recording of original document information by digital facsimile, as well as signal processing and communication control. System performance of the prototype system has been evaluated experimentally, and based upon the evaluation, design parameters for a full-fledged operational system have been described.