The 73K222BL is a highly integrated single-chip modem IC which provides the functions needed to construct a CCITT V.22, V.21, Bell 212A and Bell 103, compatible modem, capable of 1200 bit/s fullduplex operation over dial-up lines. The 73K222BL is an enhancement of the 73K222AL single-chip modem which adds the hybrid hook switch control, and driver to the 73K222AL. In Bell 212A mode, the 73K222BL provides the normal Bell 212A and Bell 103 functions and employs a 2225 Hz answer tone. The 73K222BL in V.22 mode produces either 550 or 1800 Hz guard tone, recognizes and generates a 2100 Hz answer tone, and allows 600 bit/s V.22 or 0-300 bit/s V.21 operation. The device integrates analog, digital, and switched-capacitor array functions on a single substrate, offering excellent performance and a high level of functional integration in a 32-Lead PLCC and 44-Lead TQFP package. It operates from a single +5 V supply.