--- title: "Waveforms for 111100011100110" subject: "Data Communication" chapter: 5 key: "semester_5/data_communication:line-coding-111100011100110" source: https://www.bctengineer.com/q/semester_5/data_communication/line-coding-111100011100110 site: BCT Engineering --- # Waveforms for 111100011100110 Data Communication · Chapter 5: Data Encoding and Modulation - Asked in: 2072 Kartik, 10 marks - Video: [Signal Encoding 1: Digital Signals](https://www.youtube.com/watch?v=i_TLLACZuRk) — Jacob Schrum - Answer checked by Claude Sonnet 5.5 on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_5/data_communication/line-coding-111100011100110 - Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-5 ## Question Design (a) RZ (b) NRZ-L (c) NRZ-I (d) AMI waveforms for the data sequence 111100011100110. ## Short answer RZ: polar, pulse returns to zero mid-bit; 1=+V half, 0=-V half. NRZ-L: 1=+V, 0=-V. NRZ-I: toggle at start of 1, no change for 0. AMI: 0=0V, 1s alternate +V and -V starting +V. ## Answer Bit stream: 1 1 1 1 0 0 0 1 1 1 0 0 1 1 0 (15 bits, drawn in two rows) **Conventions used** (state these in the exam, as books differ): level before the first bit is low (-V); NRZ-L/RZ: 1 = +V, 0 = -V (unipolar: 0 = 0 V); NRZ-I: a 1 toggles the level at the start of the bit, a 0 keeps it; RZ: the pulse returns to zero in the middle of the bit; Manchester: 1 = low-to-high and 0 = high-to-low transition at mid-bit; differential Manchester: always a mid-bit transition, an extra transition at the start of the bit for a 0 and none for a 1; AMI: 0 = 0 V, 1s alternate +V and -V starting with +V. #### RZ ```text 1 1 1 1 0 0 0 1 +V --| |-| |-| |-| |-| 0 |-| |-| |-| |-| |-| |-| |-| |- -V |-| |-| |-| 1 1 0 0 1 1 0 +V |-| |-| |-| |-| 0 | |-| |-| |-| |-| |-| |-| |- -V |-| |-| |-| ``` #### NRZ-L ```text 1 1 1 1 0 0 0 1 +V ----------------| |--- 0 | | -V |-----------| 1 1 0 0 1 1 0 +V --------| |-------| 0 | | | -V |-------| |--- ``` #### NRZ-I ```text 1 1 1 1 0 0 0 1 +V ----| |---| |--- 0 | | | | -V |---| |---------------| 1 1 0 0 1 1 0 +V | |-----------| |------- 0 | | | | -V |---| |---| ``` #### AMI ```text 1 1 1 1 0 0 0 1 +V ----| |---| |--- 0 | | | |-----------| -V |---| |---| 1 1 0 0 1 1 0 +V | |---| |---| 0 | | |-------| | |--- -V |---| |---| ``` AMI pulses: + - + - 0 0 0 + - + 0 0 - + 0. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. In NRZ-I as used in this answer, what does each bit do to the signal level? A. A 1 toggles the level at the start of the bit; a 0 keeps the level B. A 0 toggles the level; a 1 keeps the level C. A 1 is +V and a 0 is -V for the whole bit D. Both 1 and 0 cause a transition in the middle of the bit Answer: A. NRZ-I is differential: a 1 causes a transition at the start of the bit and a 0 leaves the level unchanged. (Key point: NRZ-I rule) 2. For 1 1 1 1 0 0 0 1 ..., what are the AMI pulses for the first four 1s and the next 1 after the three 0s? A. + + + + then + B. + - + - then + C. + - + - then - D. + 0 - 0 then + Answer: B. AMI alternates polarity for every 1, starting with +V, so the 1s are + - + - and the fifth 1 is + again; 0s stay at 0 V. (Key point: AMI polarity) 3. What distinguishes the RZ waveform from NRZ-L? A. RZ uses three voltage levels with alternating 1s B. RZ has a transition in the middle of every bit in a fixed direction C. RZ changes level only when the bit is 1 D. The pulse returns to zero in the middle of the bit Answer: D. In RZ the signal returns to 0 V at mid-bit, so a pulse occupies only half the bit time. (Key point: RZ definition) ## Related in Data Communication - [Encode 10101111000011 with NRZ, RZ, AMI, Manchester](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-10101111000011) — Data Communication, chapter 5 - [Encode 1101001 with polar NRZ, AMI, Manchester](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-1101001) — Data Communication, chapter 5, asked 3× - [Line coding: polar RZ and bipolar AMI](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-polar-rz-ami) — Data Communication, chapter 5 - [Line coding waveforms for 1101110111](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-1101110111) — Data Communication, chapter 5 - [Waveforms for 1111000111](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-1111000111) — Data Communication, chapter 5 - [AMI and Manchester for 011010001](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-011010001) — Data Communication, chapter 5 ## Related in other subjects - [Line coding 1011001010 (polar NRZ, polar RZ, Manchester, AMI)](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aline-codes-1011001010) — Communication Systems, chapter 6, asked 8× - [Line coding 1001001101 (polar NRZ, polar RZ, Manchester, AMI)](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aline-codes-1001001101) — Communication Systems, chapter 6, asked 8× - [Line coding 1001101101 (unipolar NRZ, polar RZ, AMI, Manchester)](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aline-codes-1001101101) — Communication Systems, chapter 6, asked 8× - [Line coding 1101010111 (polar NRZ, polar RZ, Manchester, AMI)](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aline-codes-1101010111-polar-ami) — Communication Systems, chapter 6, asked 8×