DTMFR-tist

DTMF

• This circuit decode frequency which is generated when key is pressed.

• The dial tone we heard when we pick up the phone set is call Dual Tone Multi-Frequency, DTMF in short.

• A complete communication consist of the tone generator and the tone decoder.

Application

• As a remote control.• Phone line transmission operation.

MOBILE JACKDTMF

CONTROLLER

D3

D2

D1

D0

1209 Hz 1336 Hz 1477 Hz 1633 Hz

697 Hz

1 2 3 A

770 Hz

4 5 6 B

852 Hz

7 8 9 C

941 Hz

* 0 # D

SMS Related AT Commands

AT It is used to test the connection.

AT+CMGF=1It is used to instruct the modem to operate in text mode. AT+CMGF=0 will instruct the modem to operate in PDU mode.

AT+CMGS="mobile number"

It is used to send a text message. It accepts the recipient mobile number. As soon as this command is accepted the modem waits for the message content. The text message has to be sent sequentially and terminated by the char 0x1A.

AT+CMGW="mobile number"

It is used to store a message in the memory. After execution it returns an index for the message stored. Eg: AT+CMGW=1 . Here 1 is the index for the saved message. Later this index is used to process the message like deleting it or forwarding to the recipient number.

AT+CMGD=2

It is used to delete a message from the storage. The index of the stored message is used to delete it. Above command deletes the message with index 2.