--- title: "Waveforms for 1111000111" subject: "Data Communication" chapter: 5 key: "semester_5/data_communication:line-coding-1111000111" source: https://www.bctengineer.com/q/semester_5/data_communication/line-coding-1111000111 site: BCT Engineering --- # Waveforms for 1111000111 Data Communication · Chapter 5: Data Encoding and Modulation - Asked in: 2073 Chaitra, 2+2+2+2 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-1111000111 - Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-5 ## Question For a binary data sequence 1111000111 sketch (a) NRZ-I waveform, (b) AMI waveform, (c) RZ waveform and (d) Manchester waveform. ## Short answer NRZ-I: toggle at start of each 1, keep level for 0 (initial low). AMI: 0=0V; 1s alternate +V and -V starting +V. RZ: polar, return to zero mid-bit; 1 is +V half, 0 is -V half. Manchester: 1 low-to-high mid-bit, 0 high-to-low. ## Answer Bit stream: 1 1 1 1 0 0 0 1 1 1 **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. #### NRZ-I ```text 1 1 1 1 0 0 0 1 1 1 +V ----| |---| |---| |--- 0 | | | | | | -V |---| |---------------| |---| ``` #### AMI ```text 1 1 1 1 0 0 0 1 1 1 +V ----| |---| |---| |--- 0 | | | |-----------| | | -V |---| |---| |---| ``` #### RZ ```text 1 1 1 1 0 0 0 1 1 1 +V --| |-| |-| |-| |-| |-| |-| 0 |-| |-| |-| |-| |-| |-| |-| |-| |-| |- -V |-| |-| |-| ``` #### Manchester ```text 1 1 1 1 0 0 0 1 1 1 +V |-| |-| |-| |---| |-| |-| |-| |-| |- 0 | | | | | | | | | | | | | | | | | -V --| |-| |-| |-| |-| |-| |---| |-| |-| ``` AMI pulses: + - + - 0 0 0 + - + (the 1s alternate: + - + - then, after the zeros, + - +). ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. AMI of 1111000111: A. + - + - 0 0 0 + - + B. + + + + 0 0 0 + + + C. + - + - 0 0 0 - + - D. + - + - 0 0 0 + + + Answer: A. Alternate across zeros. (Key point: AMI) 2. NRZ-I during 000: A. Toggles each bit B. Level stays the same C. Goes to 0 D. Mid-bit transition Answer: B. 0 keeps level. (Key point: NRZ-I) 3. In RZ a 0 is: A. +V then 0 B. 0 V C. -V then 0 D. +V Answer: C. Convention. (Key point: RZ) 4. Manchester has transition: A. Only on 1s B. Never C. Only on 0s D. Every bit at mid-bit Answer: D. Self-clocking. (Key point: Manchester) ## 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 waveforms for 1101110111](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-1101110111) — 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 - [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 - [Encode 10010110001 with NRZ-L, NRZ-I, diff. Manchester](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-10010110001) — 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×