Method of and apparatus for monitoring digital transmission systems in which line transmission errors are detected
AssigneeNorthern Telecom Limited
InventorWayne D. Grover
Life of this patent
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Abstract
A periodically reset flip-flop is set when an error is detected in the bit stream of a digital transmission link being monitored. A counter is incremented in response to each period during which the flip-flop is set and is decremented in response to a plurality of periods during each of which the flip-flop is not set. An alarm signal is produced if the count reaches a certain value. In the presence of the alarm signal, the number of error-free periods which must occur to decrement the counter is increased. The arrangement is less sensitive to error bursts causing false alarms than bit-error-rate monitoring arrangements.
Claims12
A method of monitoring a digital transmission system in which errors are detected, comprising:
- defining periods during each of which a plurality of errors may occur;
- determining whether or not at least one error occurs in each of said periods;
- in respect of each period, incrementing a digital value in a direction which is dependent upon the result of the determination;
- and
- producing an output signal in response to the digital value having a predetermined level.
Apparatus for monitoring a digital transmission system in which errors are detected, comprising:
- timing means for defining periods during each of which a plurality of errors may occur;
- bistable means arranged to be set from a first state to a second state in response to detection of an error during a period defined by the timing means;
- means responsive to the end of each period for incrementing a digital value in a first or second, opposite, direction in dependence upon the state of the bistable means at the end of the period;
- and
- means for producing an output signal in response to the digital value reaching a predetermined level.
Dependencies are inferred from the claim text.