The MSM7502, developed especially for low-power and multi-function applications in touchtone telephone sets and digital telephone terminals of digital PBXs, is a single +5 V power supply CODEC device. The device consists of the analog speech paths directly connectable to a handset, the calling circuit directly connectable to a piezosounder, the push-button key scanning interface between push buttons and control processors, the dial tone generator, the m-law/A-law CODEC, and the processor interface. The functions can be controlled via 8-bit data bus. For the CODEC of the MSM7502, an MSM7543 is used as a core CODEC, so the MSM7502 provides the available bit clock range wider than the family product MSM6895. In addition, the MSM7502 performs the greater key interface function and offers the upgraded side-tone level, receive level, and speaker pre-amplifier output level.