dramrattan
Member
Ok i have found this interesting ring detection circuit from:
Detecting a telephone RING 1 Electronic Circuit - CircuitsArchive
As it is well explained, the first circuit detects ringing but i want to be able to count the number of rings that occured as well as ring detection so that i could open the telephone line when the specified ring count is reached in order to control the activation of an electrical device using the telephone keypad.
I found the attached article which uses the 4N25 Opto-Coupler for Ring detection just like the link above but it also incorporates ring counting. I don't understand how the counting is obtained from the circuit. It is referred to as the Optic Isolation unit in the article. I thought after reading the 4N25 datasheet, all that is needed at the output of the Opto-Coupler is a pull up resistor of about 10K depending on the incoming ringing voltage. However, i notice four resistors together with a transistor at the output of the 4N25 in this attached article.
Are those four resistors and transistor used to determine ring count?...And if so, could someone please explain it to me like how the ring detection is explained in the above link (i.e. why is each of the four resistor is used and the transistor so i could calculate my own values for my design project). I would appreciate it very very very much.
Regards.
Detecting a telephone RING 1 Electronic Circuit - CircuitsArchive
As it is well explained, the first circuit detects ringing but i want to be able to count the number of rings that occured as well as ring detection so that i could open the telephone line when the specified ring count is reached in order to control the activation of an electrical device using the telephone keypad.
I found the attached article which uses the 4N25 Opto-Coupler for Ring detection just like the link above but it also incorporates ring counting. I don't understand how the counting is obtained from the circuit. It is referred to as the Optic Isolation unit in the article. I thought after reading the 4N25 datasheet, all that is needed at the output of the Opto-Coupler is a pull up resistor of about 10K depending on the incoming ringing voltage. However, i notice four resistors together with a transistor at the output of the 4N25 in this attached article.
Are those four resistors and transistor used to determine ring count?...And if so, could someone please explain it to me like how the ring detection is explained in the above link (i.e. why is each of the four resistor is used and the transistor so i could calculate my own values for my design project). I would appreciate it very very very much.
Regards.