Other known protocols are mono directional Clock and Data or bidirectional OSDP (RS 485), RS 232 or UART. The earliest card formats were up to 64 bits long. As demand has increased, bit size has increased to continue to provide unique numbers. Often, the first several bits can be made identical; these are called facility or site codes. The idea is that company A has a facility code of "xn" and a card set of 0001 through 1000 and company B has a facility code of "yn" and a card set also of 0001 through 1000. For smartcards, a numbering system is internationally harmonized and allocated by Netherlands-based NEN (registration authority) according to ISO/IEC 6523 and ISO/IEC 15459 standards.