Hello Shahzad,

"...what are the specific issues to consider when designing a device for the telephone network in a specific country."

I suggest you read Zarlink's DAA application note. It contains lots of information about those issues.

You can indeed design with the MH88422 and choose the appropriate version for the country it is supposed to be used in. Alternatively, you can also use the MH88437, which can be 'programmed' with a few external components to comply with the requirements of any country.

Regards,
Rob.