Public switched data network

A public switched data network (PSDN) is a publicly-available packet-switched network, distinct from the PSTN.

Originally this term referred only to Packet Switch Stream (PSS), an X.25-based packet-switched network, mostly used to provide leased-line connections between local area networks and the Internet using permanent virtual circuits (PVCs). Today, the term may refer not only to Frame Relay and Asynchronous Transfer Mode (ATM), both providing PVCs, but also to Internet Protocol (IP), GPRS, and other packet-switching techniques.

PSTN (Public Switched Telephone Network)

Definition: PSTN is the global collection of interconnects originally designed to support circuit-switched voice communication. The PSTN provides the traditional Plain Old Telephone Service (POTS) to residences and many other establishments. Parts of the PSTN are also utilized for DSL, VoIP and other Internet-based network technologies.

Switching in computer networks

A network switch or switching hub is a computer networking device that connects network segments.
The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer (layer 2) of the OSI model. Switches that additionally process data at the network layer (Layer 3) and above are often referred to as Layer 3 switches or multilayer switches. The term network switch does not generally encompass unintelligent or passive network devices such as hubs and repeaters.

Linear Variable Differential Transformers (LVDTs)

What is Linear Displacement Measurement?

Linear displacement is movement in one direction along a single axis. A position or linear displacement sensor is a device whose output signal represents the distance an object has traveled from a reference point. A displacement measurement also indicates the direction of motion.  A linear displacement typically has units of millimeters (mm) or inches (in.) and a negative or positive direction associated with it.

Microturbines

Introduction and Summary

Microturbines are small electricity generators that burn gaseous and liquid fuels to create highspeed rotation that turns an electrical generator. Today’s microturbine technology is the result of development work in small stationary and automotive gas turbines, auxiliary power equipment, and turbochargers, much of which was pursued by the automotive industry beginning in the 1950s. Microturbines entered field testing around 1997 and began initial commercial service in 2000.