vinodquilon
Member
Pls find the pdf attachment ('CI-2-DTMF').
After setting the circuit (using mt8870) in differential configuration, when I switch on the circuit LEDs 1,2,3, & 4 are all suddenly ON without detecting ring volt and key press. And remain in the same ON state after pressing * and then decimal keys from the telephone keypad on caller end.
So, I am tempted to test in single-ended configuration (see second attached file 'dtmf'). I manually short R18 to accept remote calls. But same problem arises.
After setting the circuit (using mt8870) in differential configuration, when I switch on the circuit LEDs 1,2,3, & 4 are all suddenly ON without detecting ring volt and key press. And remain in the same ON state after pressing * and then decimal keys from the telephone keypad on caller end.
So, I am tempted to test in single-ended configuration (see second attached file 'dtmf'). I manually short R18 to accept remote calls. But same problem arises.