---
title: "Pulse dialing waveform for number 401"
subject: "Telecommunications"
chapter: 1
key: "semester_8/telecommunications:pulse-dialing-waveform-401"
source: https://www.bctengineer.com/q/semester_8/telecommunications/pulse-dialing-waveform-401
site: BCT Engineering
---

# Pulse dialing waveform for number 401

Telecommunications · Chapter 1: Telecommunication Networks

- Asked in: 2079 Bhadra, 1 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/telecommunications/pulse-dialing-waveform-401
- Whole chapter: https://www.bctengineer.com/md/semester_8/telecommunications/chapter-1

## Question

Draw the pulse dialing waveform for the number 401.

## Short answer

For 401: 4 loop-break pulses for digit 4, inter-digit pause, 10 pulses for 0, pause, then 1 pulse for 1. Each pulse period is 100 ms (break 66.7 ms, make 33.3 ms), inter-digit pause ~200 ms.

## Answer

Each digit is sent as that many loop **breaks** (0 = 10 breaks) at 10 pulses per second (period 100 ms, break 66.7 ms, make 33.3 ms), with an inter-digit pause between digits.

```text
Loop current (high = make/closed, low = break):
         4 pulses        10 pulses (digit 0)  1 pulse
 ───┐ ┌┐ ┌┐ ┌┐ ┌──────┐ ┌┐ ┌┐ ... ┌┐ ┌──────┐ ┌──────
    └─┘└─┘└─┘└─┘  IDP └─┘└─┘└ ... ┘└─┘  IDP └─┘
     digit 4             digit 0           digit 1
 One pulse = 100 ms: break 66.7 ms + make 33.3 ms
 IDP = inter-digit pause (~200 ms or more)
```

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How many loop breaks make up the number 401?
   A. 5
   B. 6
   C. 15 (4 + 10 + 1)
   D. 14
   Answer: C. 4 gives 4 breaks, 0 gives 10, 1 gives 1. (Key point: Pulse count)

2. In one pulse of 100 ms, the break and make times are
   A. Break 33.3 ms, make 66.7 ms
   B. Break 50 ms, make 50 ms
   C. Break 100 ms, make 10 ms
   D. Break 66.7 ms, make 33.3 ms
   Answer: D. The break:make ratio is 2:1 at 10 pps. (Key point: Pulse timing)

3. What separates the digits in the waveform?
   A. An inter-digit pause of about 200 ms or more
   B. Nothing; pulses run continuously
   C. A DTMF tone
   D. A break of 33 ms
   Answer: A. The pause lets the exchange tell digits apart. (Key point: Separation)

## Related in Telecommunications

- [DTMF vs pulse dialing and DTMF design](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Adtmf-vs-pulse-design) — Telecommunications, chapter 1, asked 2×
- [Rotary dial dialing time calculation](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Arotary-dial-time-calculation) — Telecommunications, chapter 1

## Related in other subjects

- [Pulse shaping circuit and output waveform](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Apulse-shaping-circuit) — Basic Electronics Engineering, chapter 2
- [Self and line commutation; minimum gate pulse width](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_electronics%3Aself-line-commutation-gate-pulse) — Power Electronics, chapter 1