A 4-wire solid-state switching system: Subscriber instruments

This paper will discuss four basic types of subscriber instruments for an electronic solid-state switching system which meet functional requirements of a communications complex to provide the interface between the switching-system and voice-frequency inputs; these basic types include multiline instruments, manual-and remote-controlled teletype, radio, and other unattended machines. Unique packaging techniques and component standardization resulted in full compliance with military, mechanical, environmental, and reliability requirements. Compatibility requirements for a switching network were achieved by using ample safety factors in satisfying limits on signaling and transmission. A high degree of simplification was obtained by choosing d-c supervisory circuits between subscriber stations and switching centers and by using standard solid-state logic elements.