Is possible to send data over a phone line without a modem??

[eltonjohn]

rat_ring

Ok a have this IDEA ,, i want to send a code over the PHONE line ..the device has to be very small ..TINY .. and real cheap .. very cheap!
I dont want to put a modem ....(in the general sense!)
It will dial .. and then send the code an receive some other code .
I have the DTMF's routines that produce the codes and with a 1-bit AD
converter i'm able to reconize the code .. So now is a matter of interfacing this thing to the line .. I'm thinking to do it optically ..?
What do you think?

 

[hot_chmock]

sending data from microcontroller over phone line

It you use 2 tones with <> frequency one for 0 and one for 1 it will be very simple very cheap and very slow.

hc

 

[C-Man]

Re: Is possible to send data over a phone line without a mod

Maybe you can get lucky here:
A group of PIC microcontroller enthusiasts dedicated to open
distribution of real world telecommunications applications running on the lowest
cost Flash PIC hardware.

Why not visit our website at www.geocities.com/kenboak/rat_ring.html

To learn more about the rat_ring discussion group, please visit the
Yahoo site:

https://groups.yahoo.com/group/rat_ring

They use a PIC to cummunicate via phoneline.

best regards

 

[artem]

You do not need optical coupling , if things what your mcu is monitoring on do not require that .

That means you can supply you mcu directly from phone line , and if it is low power mcu , you can get power even when no call is ongoing (but dc-dc converter will be needed ). I do not remember exact current (in theory POTS line is current source) may be in range 15-25 ma . So , if you get 12 V at that current - you have 200 mW of power .
Simplest way is to get power
via serialy zener and resistor . Send and receive can be done directly from line via decoupling capacitor , connected to line where resistor is present . That is for half duplex connection . But if you need something more sophisticated and/or full duplex
mode - hybrid transformer and other wires must be added (transistor or transformer based ).
As a base you can use electornic telephone
design . The hybrid transformer , input (microphone)
output (speaker), hook on/off circuits - all are there . You canuse only transistors or simple chips to make it cheap .

Optocoupling also possible - but it will just add coupling circuits to the mentioned above .

 

[bobcat1]

Re: Is possible to send data over a phone line without a mod

What you need is a DAA circuit to interface the phone line

there are meny company who produce DAA (slic)chip set who operate directly from the phone line

Goto **broken link removed**


enjoy


bobi

 

[birumher]

Re: Is possible to send data over a phone line without a mod

You can use DTMF but it will be very very slow.
You must "invent" a protocol.

For example
* - Start bit
# - Stop bit
1 - 00
2 - 01
3 - 10
4 - 11
With this protocol you can send A byte with 6 tones

For example if yo want to send "A" '1000001'

yo must send *3112#

 

[Z80]

Re: Is possible to send data over a phone line without a mod

Can't you use the V23 protocol? It's the simplest, slowest protocol for data over standard phone lines.