MT8870 DTMF Decoder Protection Circuit

Discussion in 'General Electronics Chat' started by kygh_qin, Dec 5, 2009.

  1. kygh_qin

    Thread Starter New Member

    Nov 29, 2009
    i m currently working on a caller id project using PIC18F4455. MT8870 is used in this project. however, Fixed telephone line cannot be connected to MT8870 directly. i had found two types of protection circuit from the internet. but i dont know which one is better and dont know how they works actually.