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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):

Digit0119144414630
Pulses101191444146310

Total pulses =58= 58.

Nominal rate (10 pps): pulse period T=1/10=100T = 1/10 = 100 ms (make 33.3 ms, break 66.7 ms).

t=13×600+58×100+12×200=7800+5800+2400=16000 ms=16.0 s\begin{aligned} t &= 13 \times 600 + 58 \times 100 + 12 \times 200 \\ &= 7800 + 5800 + 2400 \\ &= 16000\ \text{ms} = 16.0\ \text{s} \end{aligned}

Worst case (slowest rate, 10% tolerance → 9 pps): T=1/9=111.1T = 1/9 = 111.1 ms.

tmax=7800+58×111.1+2400=7800+6444.4+2400=16644.4 ms\begin{aligned} t_{max} &= 7800 + 58 \times 111.1 + 2400 \\ &= 7800 + 6444.4 + 2400 = 16644.4\ \text{ms} \end{aligned}

(At the fastest rate, 11 pps, T=90.9T = 90.9 ms and tmin=15472.7t_{min} = 15472.7 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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