DTMF dial tone

[Josuetas]

It can´t be simplier than this,

By the way those modems you have must surely have the transformer you need.

Now forget about the ugly picture!

Pay attention to this fact: the line will remain Off-hook as long as it is connected to the
transformer, you might need a relay to disconnect the line from the Transformer.



DAA is the device that implements this transformers with silicon, it also gives you more functionality like ring detection and off-hook switch. It might be more expensive than the simple schematic, wich by the way complies with all requirements of ITU.