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DTMF decoder 2 Circuit

The DTMF decoder 2 is a useful tool used for decoding DTMF (Dual Tone Multi frequency) generated by telephones. The decoded digits are viewed on a 16x2 LCD screen. The DTMF decoder can be directly connected to a Serial port to view the digits in HyperTerminal on a computer. The decoder stores the last 234 received digits in EEPROM. The contents of EEPROM can be viewed on the LCD screen via two scroll buttons. Total power consumption is 12mA. The DTMF decoder has two inputs. A RJ11 jack for connecting to the phone line and a 1/8" audio jack for connecting to a scanner, tape recorder or other audio output device.

The list includes parts for the DTMF Decoder. All part numbers are for Digikey unless their is a link to another supplier.

Quantity Value Description Digikey Part No. Component
1 78L05 +5V Regulator 296-1365-1-ND U1
1 MCP120 Supply Supervisor MCP120-450DI/TO-ND U5
1 AT90S2313 Microprocessor AT90S2313-10PI-ND U2
Alternative Micro ATTINY2313-20PI-ND U2
1 MT8870DE DTMF Decoder E-SONIC U4
1 4N25 Opto-isolator 160-1300-5-ND U3

1 10uF Dielectric P10316-ND C1
4 4.7 uF
P1199-ND C6,7,9,10
3 0.1 uF
P4525-ND C2,4,8
2 18pF
P4840-ND C11,C12

1 4.7K 1/4 Watt 4.7KQBK-ND R4
3 10K 1/4 Watt 10KQBK-ND R1,2,6
2 47K 1/4 Watt 47KQBK-ND R7,R8
1 390K 1/4 Watt 390KQBK-ND R9
1 20K POT Vertical POT 36G24-ND R5

1 16x2 LCD 73-1025-N LCD
RJ 11 Jack CCM9000-ND Phone
1/8 Audio Jack CP-3543N-ND Audio
9V Connector BS6I-HD-ND Batt
20-pin Socket A9420-ND
Push Buttons P8006S-ND S1,S2
2 0.1" 7-pin Header strip WM4005-ND
1 3.579545 Mhz 3.58 Mhz Crystal 300-6001-ND Y1
1 Female DB9 Connector A2047-ND DB9

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