Patent ID: 6642845
Filing Date: 2003-11-04
Classification: H04B,H04J

Abstract:
A signal quality monitoring device for monitoring quality of a signal received by a transmitter and, when the signal is of low quality, selectively issuing one of two alarms with different grades in accordance with a grade of low quality of the signal, comprising:a first-grade alarm producing/canceling section for successively discriminating whether the current signal is in a first grade of low quality and, when the current signal has stayed in the first grade of low quality for a first producing time period, producing continuous output of a first-grade alarm while, when the result of the discriminating becomes negative and the current signal has stayed off the first grade of low quality for a first canceling time period, canceling the continuous output of the first-grade alarm; a second-grade alarm producing/canceling section for successively discriminating whether the current signal is in a second grade of low quality and, when the current signal has stayed in the second grade of low quality for a second producing time period, producing continuous output of a second-grade alarm while, when the result of the discriminating becomes negative and the current signal has stayed off the second grade of low quality for a second canceling time period, canceling the continuous output of the second-grade alarm; and an alarm holding section for, when a grade of low quality of the current signal shifts from one to the other of the first and the second grades and the corresponding one of said first-grade alarm producing/canceling section and said second-grade alarm producing/canceling section has canceled the continuous output of the corresponding alarm as a consequence of expiration of the corresponding canceling time period, if the other of said first-grade alarm producing/canceling section and said second-grade alarm producing/canceling section discriminates that the current signal is in the other grade of low quality, holding the continuous output of the one alarm regardless of the cancellation by said one alarm producing/canceling section, until the other alarm producing/canceling section produces the continuous output of the corresponding other alarm as a consequence of expiration of the corresponding producing time period.