dtmf circuit


Posted on Feb 5, 2014

This article describes how to build a general purpose DTMF decoder with a low-price chip from MITEL. The circuit supports DTMF squelch based on 3 digits station ID (full 999 combination). It also supports decoding of 4 additional commands - station ID plus one more digit which can be used to perform remote control on external devices (on/off or si


dtmf circuit
Click here to download the full size of the above Circuit.

ngle shoot trigger operation ). One expansion port is included to provide future development. Core of the whole equipment is the MT8870 DTMF decoder. This is a state of art single chip DTMF receiver incorporating "switched capacitor filter" technology and advanced digital counting / averaging algorithm for period measurement. Conventional method of frequency decoding usually based on frequency counting or phase locking technique. These methods are time consuming and inaccurate when handling unsteady complex signal. Switched capacitor filter technology based on a completely different approach. It works on the theory that any A. C. signal are rapid changes of potential energy with repect to specific time factor. A. C. components, provided that they bear the same frequency characteristic, will have the same timing on instantaneous potential variation. For example, a signal of frequency 1 Hz will experience peak positive value every one second. - the duration of 1 sec. will be constant among any A. C. signal bearing frequency 1 Hz, even though they have different wave forms. Suppose a circuit is designed to sample the potential value of a signal at preset intervals ( say, at exactly 90 degree phase shift timing for a specific frequency ). If the total sum of all samples always experience zero while signal really present. We can conclude that an A. C. component of that specific frequency has been identified. Each fixed timing...




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

remote control circuit
dtmf decoder
vehicle tracking
Astable Multivibrator using NE 555 timer IC
Johnson digital counter circuit diagram using D flip flop 7474 (3 bit/4 bit) with animation/ simulation
Low-Voltage Remote Mains Switch
CD4060 production time controller circuit diagram
Multiplicative DA converter IC inexpensive 8 DA circuit
Buffer leakage current measurement circuit diagram OPA111 INA117
Simple audio amplifier LM307 A741
XTR110 voltage - current converter circuit diagram
Complementary voltage switching Class D amplifier circuit



Top