公开(公告)号：CA1115788A

公开(公告)日：1982-01-05

申请号：CA319091

申请日：1979-01-04

Applicant: NORTHERN TELECOM INC

Inventor： SAWYER ROBERT E JR ,  DONAHUE ROBERT J

IPC: G01R19/165 ,  H03K5/153

Abstract: LEVEL SELECTIVE A-C MONITORING CIRCUIT A circuit for monitoring an a-c input signal comprising a selectable gain amplifier responsive to the input signal, an a-c to d-c converter for converting signals at the output of the selectable gain amplifier to corresponding d-c values, a first comparator for comparing said d-c values to a predetermined minimum d-c value, a second comparator for comparing the d-c values to a predetermined maximum d-c value, the predetermined maximum value corresponding to a maximum acceptable value of the input signal, a third comparator for comparing said d-c values to a predetermined absolute maximum a-c value, and feedback means connected between the output of the first comparator and the third comparator for causing the third comparator to compare the d-c values to said minimum d-c value, the predetermined absolute maximum value corresponding to an absolute maximum acceptable value of the input signal, the absolute maximum acceptable value being greater than the maximum value. -i-