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Document: Datasheet Date: 11-Mar-12 Model #: 1218 Products Page: www.sunrom.com/p-911.html
DTMF Decoder
This board decodes DTMF signal either from an audio source or phone line to 4 bit binary TTL(5V)level output. It also indicates outputs with LED.Can use directly with microcontrollers to develop various DTMF related applications like remotemonitoring, remote control, Caller ID, Auto Dialer and such.
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
Parameter Value Unit Notes
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 high
output 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.
Board has two terminals
1) DTMF Audio Input for microphone amp, FM radio receiver, Bluetooth audio receiver and such.
2) Land line phone terminal. Before connection take a Multimeter and identity the plus and minus of
your phone line. Then connect to its terminal of Phone+ and Phone- accordingly.
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Schematic of board
Sample Application
Here is an application used with microcontroller which displays received DTMF tone on sevensegment display.
Program source code download
http://www.sunrom.com/files/1218.zip
TitleCode RevDate: Sheet of
1218 1DTMF Decoder
Sunrom Technologies http://www.sunrom.com
1 1Saturday, March 06, 2010
+ C3
100uF 25V
R2
100K
R1100K
C2100nF
VT
DTMF Audio Input Data Out
CN3SIP2
12
C5
100nF
Phone Line
+
-
U1MT8870
Q111
Q212
Q313
Q4
14
OSC17
OSC28
OE
10
VREF4
IN+
1
IN-2
GS3
IC15
IC26
VSS
9
VDD
18
STD15
ST/GT17 EST16
Y13.5795 MHZ CRYSTAL
R3270K
VCC
VCC
C1100nF
R4470R
R5470R
R6470R
R7470R
R8470R
D2LED
D3LED
D4LED
D5LED
D1LED
C4100nF
VCC
CN2SIP8
1234
5678
VCC
Q3
Q4
Q2Q1
CN1SIP2
12
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Related Links
Datasheet of MT8870http://www.sunrom.com/files/M8870-R3.pdf
About DTMFhttp://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling
Google result of MT8870, Many useful referenceshttp://www.google.co.in/search?q=MT8870
http://www.sunrom.com/http://www.sunrom.com/files/M8870-R3.pdfhttp://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signalinghttp://www.google.co.in/search?q=MT8870http://www.google.co.in/search?q=MT8870http://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signalinghttp://www.sunrom.com/files/M8870-R3.pdfhttp://www.sunrom.com/