The 73K322L is a highly integrated single-chip modem IC which provides the functions needed to construct a CCITT V.23, V.22 and V.21 compatible modem, capable of 1200 or 0-300 bit/s full-duplex operation or 0-1200 bit/s half-duplex operation with or without the back channel over dial-up lines. The 73K322L is an enhancement of the 73K221L singlechip modem with performance characteristics suitable for European and Asian telephone systems. The 73K322L produces either 550 or 1800 Hz guard tone, recognizes and generates a 2100 Hz answer tone, and supports V.21 for 300 Hz FSK operation. It also operates in V.23, 1200 bit/s FSK mode. The 73K322L integrates analog, digital, and switchedcapacitor array functions on a single substrate, offering excellent performance and a high level of functional integration in a single 28-pin PLCC or DIP package. The 73K322L operates from a single +5V supply with very low power consumption.