Unusual types of gramophone records Hi-Fi was a system of proprietary records and players designed for use in automobiles, utilizing a slower play speed and high stylus pressure. With their origin stretching back to the dawn of recorded sound at the turn of the 20th century, flexible recording media have been made from a variety of materials including foil, paper, and–in the 1950s–thin flexible vinyl known as flexi discs. Thin, flexible paper-based records were briefly popularized in the 1930s by Hit of the Week Records and Durium Records. "Melody Cards" were popular in the late 1950s. They took the form of an oversized rectangular postcard
Lithium polymer battery the touch, they can still contain 30% to 50% liquid solvent. In this regard, how to really define what a "polymer battery" is remains an open question. Other terms used in the literature for this system include hybrid polymer electrolyte (HPE), where "hybrid" denotes the combination of the polymer matrix, the liquid solvent and the salt. It was a system like this that Bellcore used to develop an early lithium-polymer cell in 1996, which was called "plastic" lithium-ion cell (PLiON), and subsequently commercialised in 1999. A solid polymer electrolyte (SPE) is a solvent-free salt solution in a polymer medium. It