A telephone exchange has 9000 subscribers. If the number of calls originated during the busy hour is 10,000 in one hour, what is the average calling rate per subscriber?
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A0.9 calls per subscriber
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B10/9 calls per subscriber
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C0.81 calls per subscriber
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D0.1 calls per subscriber
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E1 call per subscriber
Answer
Correct Answer: 0.9 calls per subscriber
Explanation
Introduction / Context:Traffic engineering in telephony requires understanding the offered traffic load, measured in Erlangs or as an average call rate. Busy-hour call attempts per subscriber are key for designing capacity of switches and trunks.
Given Data / Assumptions:
- Total subscribers = 9000.
- Total calls in peak hour = 10,000.
Concept / Approach:
Calling rate per subscriber = total calls / number of subscribers. This provides the average number of originated calls per subscriber during the busy hour.
Step-by-Step Solution:
Total calls = 10,000.Subscribers = 9000.Rate = 10,000 / 9000 = 1.111… calls per subscriber.Rounded or expressed as ≈ 1.11 calls per subscriber; however in many engineering exam contexts, they approximate it as 10/9 ≈ 1.11.Verification / Alternative check:
Divide precisely: 10,000 ÷ 9000 = 1.111. Thus 10/9 is the exact expression.
Why Other Options Are Wrong:
- 0.9 or 0.81 or 0.1: numerical errors, not the correct ratio.
- 1 call: underestimates slightly; true ratio is greater than 1.
Common Pitfalls:
Misinterpreting the calling rate as calls per second instead of per subscriber per hour; forgetting to normalize by subscriber count.
Final Answer:
10/9 calls per subscriber