DS75176

The device features an output enable (OE) and send/receive (DIR) for direction control. A HIGH on OE causes the outputs to assume a high-impedance OFF-state. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.

The CM8870PI provides full DTMF receiver capability by integrating both the bandsplit filter and digital decoder functions into a single 18-pin DIP. The filter section uses a switched capacitor technique for both high and low group filters and dial tone rejection. The CM8870 decoder uses digital counting techniques for the detection and decoding of all 16 DTMF tone pairs into a 4-bit code. This DTMF receiver minimizes external component count by providing an on-chip differential input ampli-fier, clock generator, and a latched three state interface bus. The on-chip clock generator requires only a low cost TV crystal or ceramic resonator as an external component.

MAX232 is a communication IC. It is used to convert TTL Signals to RS232 Signal and vice versa.?MAX232?provides RS-232 voltage level outputs (approx. ? 7.5 V) from a single 5 V supply via on-chip charge pumps and external capacitors. This makes it useful for implementing RS-232 in devices that otherwise do not need any voltages outside the 0 V to 5 V range, as power supply design does not need to be made more complicated just for driving the RS-232 in this case.

The receivers reduce RS-232 inputs (which may be as high as ? 25 V), to standard 5 V TTL levels. These receivers have a typical threshold of 1.3 V, and a typical hysteresis of 0.5 V.