dramrattan
Member
Hi,
The attached ciruit is used to detect when a phone goes off hook by using two voltage dividers...The pin 6 voltage is obtained by dividing the 48V across the line by 20 t0 be compared with pin 7 that is fixed at approximately 1V.
Why is such a large resistor like 10M is required as the first resistor in the voltage divider to pin 6 of the LM339 comparator?.
The attached ciruit is used to detect when a phone goes off hook by using two voltage dividers...The pin 6 voltage is obtained by dividing the 48V across the line by 20 t0 be compared with pin 7 that is fixed at approximately 1V.
Why is such a large resistor like 10M is required as the first resistor in the voltage divider to pin 6 of the LM339 comparator?.