Description

DTMF Decoder

Decodes DTMF audio signal to 4 bit binary TTL level output with LED indication. Suitable for use with microcontroller applications.

Features

•   Decodes DTMF as 4 bit binary
•   TTL level output for direct connection to microcontrollers
•   Low power 5V DC operation
•   LED indication of outputs
•   Simple to use
•   Based on excellent MT8870 IC

Applications

•   Remote Control systems
•   Caller ID applications
•   FM receiver based remote control
•   Remote control using Mobile phone

Specification

•  Operating Voltage 5 V DC Regulated power supply input
•  Operating Current 100 mA

Information

Connect regulated +5V DC supply for operation of board. Outputs Q1-4 and VT are active highoutput at 5V level. If any LED is on means that output is at high level. VT LED blinks once a new DTMF tone is received. The binary data appears at Q1 to Q4. Details of this output is on next page.Input signal can be from an audio source like microphone amplifier, FM radio receiver, wired phone line. Please note when connecting land line phone signal, do not connect ground wire of board to phone line directly. Use a 100nF capacitor in series to phone line wires at ground.

NOTE  :   100k resister Connected in series for Input  –  For  GSM Modems& Mobiles  reduce Value , If not working to  10K