- 2079 Bhadra · 3 marks
Rotary dial dialing time calculation
Short answer
Total time = rotation time (13 digits × 600 ms = 7800 ms) + pulse time (58 pulses × 100 ms = 5800 ms) + inter-digit gaps (12 × 200 ms = 2400 ms) = 16.0 s at nominal 10 pps. Worst case (9 pps, period 111.1 ms) total = 16.64 s.
Calculate the time required to dial the number 011-91-44-414630 using a rotary dial telephone. Assume the subscriber takes 600 milliseconds on average to rotate the dial for a single digit; the pulse rate is 10 pulses per second with a 10% tolerance, the inter-digit gap is 200 milliseconds, and the duty ratio of a pulse is 33%.
The total time = (dial rotation time for every digit) + (pulse time for every digit) + (inter-digit gaps). The 33% duty ratio only fixes how each pulse period is split into make (33%) and break (67%); it does not change the pulse period.
Digits and pulses (number 0119144414630, 13 digits; digit 0 gives 10 pulses):
| Digit | 0 | 1 | 1 | 9 | 1 | 4 | 4 | 4 | 1 | 4 | 6 | 3 | 0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Pulses | 10 | 1 | 1 | 9 | 1 | 4 | 4 | 4 | 1 | 4 | 6 | 3 | 10 |
Total pulses .
Nominal rate (10 pps): pulse period ms (make 33.3 ms, break 66.7 ms).
Worst case (slowest rate, 10% tolerance → 9 pps): ms.
(At the fastest rate, 11 pps, ms and ms.)
Answer: about 16.0 s at the nominal 10 pps; up to 16.64 s in the worst case (9 pps). (12 inter-digit gaps are counted, between the 13 digits.)
✓ Answer checked by Claude Opus 5.5 (high effort)
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