from an adjacent wooden box affixed to fit batteries before telephones could draw power from the telephone line itself. The Leclanché cell can not provide a sustained current for very long. In lengthy conversations, the battery would run down, rendering the conversation inaudible. This is because certain chemical reactions in the cell increase the internal resistance and, thus, lower the voltage. Zinc-carbon cell, the first dry cell Many experimenters tried to immobilize the electrolyte of an electrochemical cell to make it more convenient to use. The Zamboni pile of 1812 is a high-voltage dry battery but capable of delivering only minute currents. Various experiments were made with cellulose, sawdust, spun glass, asbestos fibers, and gelatine. In 1886, Carl Gassner obtained a German patent on a variant of the Leclanché cell, which came to be known as the dry cell because it does not have a free liquid electrolyte. Instead, the ammonium chloride is mixed with plaster of Paris to create a paste, with a small amount of zinc chloride added in to extend the shelf life. The manganese dioxide cathode is dipped in this paste, and both are sealed in a zinc shell, which also acts as the anode. In November 1887, he obtained for the same device. Unlike previous wet cells, Gassner's dry cell is more solid, does not require maintenance, does not spill, and can be used in any orientation. It provides a potential of 1.5 volts. The first mass-produced model was the Columbia dry cell, first marketed by the National Carbon Company in 1896. The NCC improved Gassner's model by replacing the plaster of Paris with coiled cardboard, an innovation that left more space for the cathode and made the battery easier to assemble. It was the first convenient battery for the masses and made portable electrical devices practical, and led directly to the invention of the flashlight. The zinc–carbon battery (as it came to be known) is still manufactured today. In parallel, in 1887 Wilhelm Hellesen developed his own dry cell design. It has been claimed that Hellesen's design preceded that of Gassner. In 1887, a dry-battery was developed by Sakizō Yai (屋井 先蔵) of Japan, then patented in 1892. In 1893, Sakizō Yai's dry-battery was exhibited in World's Columbian Exposition and commanded considerable international attention. NiCd, the first alkaline battery In 1899, a Swedish scientist named Waldemar Jungner invented the nickel–cadmium battery, a rechargeable battery