A Digital Telephone Set for ISDN

In addition to the present voice communications services, more diverse digital telephone services are in very strong demand. Among the critical system requirements for designing digital telephone sets are how to economically realize new telephone services and how to ensure the continuity of existing analog telephone services. This paper describes the system requirements from both the service and technical points of view in the design of telephone sets. Based on these requirements, it further describes a method of designing network interface and telephone function blocks. An outline of the configurations and characteristics of digital telephone sets which can be operated by remote power feeding is presented as a design example.