Abstract
Twenty-four network control operators were observed executing monitor and control tasks involving large-scale remote networks. The networks are associated with six message switching systems. The operators tasks involved responding to software generated alarm messages, and invoke network changes via a command language, to regulate input/output traffic flow. Data were collected using activity analysis sampling, command language analysis, and error analysis in order to obtain statistics on the following factors: operator work load, alarm volume per hour, operator response time per alarm, system acknowledgement time, error type and frequency.
The results indicated that the alarm volume required an operator response time of 90 seconds, which overloaded the operators. Recommendations to allocate to the software additional monitor and control tasks, and to modify the software interfaces, reducing the alarm volume, were implemented. The results of a second experiment, conducted to measure the effects of the software changes, identified a substantial improvement in operator performance, a reduction in operator workload, errors, and alarm volume. These findings led to the confirmation of several human factors principles applicable to interface design.
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