Firstly, I would like to thank to Mr Karas, I have read
your messages and I will consider those suggestions.

Secondly, to Mr Murugan AKT, thank you for your
response. The circuits follows the typical circuit
of the MT8870 as describe in the Zarlink data sheet
for the MT 8870 'the single ended' applications.
Pin 2 of the MT8870 is in series with a 100 k
resistor to a 100 nF C to one of the telephone lines.
A 100 nF C is connected to the other line of the
telphone lines to the GND of the MT8870. Two Zener
diodes of 3V3 with back to back connection is connected
to the GND and to the point of a 100k R and 100nF C
after the first line of the telephone lines.
This is in purpose to cut the high voltage of the ringing signals or other high incoming signals
to the inputs of the MT8870 to protect the chip.

I am happy to post the circuits but I don't know
how to post the circuit in this boards. Please send
me your email address and I will send you the
circuits in form of Microsoft office Word Ver 7.
my e-mail addr: mikronik@mdn.prima.net.id

This asking is also to any one interrested with
the circuits, please feel free to send me your
email address.

Again, thank you in advance.