Quote Originally Posted by lerameur View Post
ok but what is off hook.
I mean I have a dual splitter from the telephone line. One line goes to a telephone and the second line will go to the Pic chip. When I need to dial from the chip, how do I do an auto hook off on the telephone line so I can use the DMTFOUT command?

k
As I already told in in the earlier reply, themoment you lift the hanset from the telephone , it is called OFFHOOK. Now in your contest- you may know that the exchange gives a voltage of 48V DC with a max current limit of 35mA. this current will flow thro the switch provided in the instrument. in your case you have to provise a trmnsformer primary loop thro' a relay contact controlled by you . then if the loop is extended , it is called OFFhook


this can be checked by inserting a DMM in DC mA range in series to one of the limbs by breaking the connection and inserting the Meter for current measurement.