The NE5900 call progress decoder (CPD) is a low cost, low power CMOS integrated circuit designed to interface with a microprocessor-controlled smart telephone capable of making preprogrammed telephone calls. The call progress decoder information to permit microprocessor decisions whether to initiate, continue, or terminate calls. A tri-state, 3-bit output code indicates the presence of dial tone, audible ring-back, busy signal, or re-order tones.