The document describes the 212 series of decoders from Holtek. It provides three key details: 1) The 212 series of decoders can decode up to 12 bits of address and data information from encoded signals transmitted by 212 series encoders. They include models with different combinations of address and data pins. 2) The decoders receive serial data from an encoder, compare the address to an internal address, and output the data if the addresses match. They check the address three times to ensure valid transmission. 3) Applications include security systems, remote controls, and other devices using radio or infrared transmission of encoded signals between encoders and decoders.