NE5900

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.

A front-end bandpass filter is accomplished with switched capacitors.  The bandshaped signal is detected and the cadence is measured prior to output decoding.  In addition to the three data bits,a buffered bandpass output and envelope output are available.  All logic inputs and outputs can interface with LSTTL, CMOS and NMOS.

Circuit features include low power consumption and easy application.  Few and inexpensive external components are required.  A typical application requires a 3.58MHz crystal or clock,470k resistor, and two bypass capacitors.  The NE5900 is effective where traditional call progress tones, PBX tones, and precision call progress tones must be correctly interpreted with a single circuit.