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transceiving data through phone line

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hm_fa_da

hm_fa_da

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hi all


i want to transmit and receive data through phone line , i have done it by DTMF tones before using MT8870(transmitter) and TP5088(receiver) ,but the bit rate was 40bit/sec ,

now is there other ICs for this application with faster data rate ?

thanks...
 

Hi
Use modem.
AT command set will help you.
It's pro.
 

hi,

I don't remember the datarate of the DTMF Tx/Rx. But the last time i read the data sheet for the Mitel, i remember each tone transmission takes 80ms, which includes the tone tx and the valid 'silent' period. Base on that, it will means being able to transmit 12.5 tone per sec. Multiply that with 4, we get 50 bits per second.

If you need a higher data rate, perhaps you can use modem instead. Please check out 'rat ring', it's a yahoo group that discusses about various telecommunication method implementing using both DTMF and V.23. Most of the codes are written for the PIC. There are codes, schematic and phone interfacing method which can be downloaded.

Thks.

chicken_feet
 

you can build FSK modem if you can't include computer (and modem card) to your project, - i see you uses ICS so i conclude modem will not be suitbale for your project- any way read this doc file about building FSK modem it may be helpful



shafee
 

DTMF tones before using MT8870(transmitter) and TP5088(receiver) ,but the bit rate was 40bit/sec ,
Click to expand...

MT8870 have 4 bit input, you must use all input, so transmit every 4 bit data. Data will send 4 * 40bit/sec = 160bit/sec
 

i have used all inputs and the bit rate was 40/sec !!!
each tone about 90mls ( 100mls )
and 4 bit , so 1sec = 4*10 = 40b/sec ,
 

halo,

hm, your calc is correct. each tone represents a symbol and each symbol can be use to represent 4 bits uniquely.
anyway, have you check out the rat ring? I have downloaded some files which describes the v23 method. no modem is being used and the data rate is 1200 baud. the sch is all there and if you have any further question, you can always post it at the group.

brgds,
chicken_feet
 

thanks to all ,

i found this good ic :CMX867 , it is really a good and high speed IC for this application , i hope i find it in market !
 

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