--- title: "Line coding waveforms for 1101110111" subject: "Data Communication" chapter: 5 key: "semester_5/data_communication:line-coding-1101110111" source: https://www.bctengineer.com/q/semester_5/data_communication/line-coding-1101110111 site: BCT Engineering --- # Line coding waveforms for 1101110111 Data Communication · Chapter 5: Data Encoding and Modulation - Asked in: 2079 Baisakh, 2+2+2+2 marks - Video: [Line Coding Techniques | RZ, NRZ, Unipolar, Polar, Bipolar & Manchester | Digital Communication](https://www.youtube.com/watch?v=daf9F9NC7zQ) — Engineering Funda - Answer checked by Claude Sonnet 5.5 on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_5/data_communication/line-coding-1101110111 - Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-5 ## Question What are the needs of line coding in data communication? Given the binary data sequence 1101110111 represent it in unipolar NRZ, polar RZ, Manchester and AMI waveform. ## Short answer Line coding provides clock recovery, DC balance, bandwidth reduction, and error detection. For 1101110111: Unipolar NRZ uses +V for 1, 0V for 0; Polar RZ uses +V then 0 for 1, -V then 0 for 0; Manchester uses low-to-high mid-bit for 1, high-to-low for 0; AMI alternates +V,-V for 1, 0V for 0, yielding +-0+-+0-+-. ## Answer #### Needs of line coding Line coding converts digital data into a digital signal that suits the channel. It is needed to: 1. Give the receiver enough transitions to recover the clock (synchronisation). 2. Remove the DC component, which cannot pass through transformers or AC-coupled links. 3. Reduce the bandwidth needed. 4. Give error detection (for example, AMI violations) and noise immunity. 5. Keep the cost and complexity of the circuits low. #### Waveforms for 1101110111 **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. #### Unipolar NRZ ```text 1 1 0 1 1 1 0 1 1 1 +V --------| |-----------| |----------- 0 |---| |---| ``` #### Polar RZ ```text 1 1 0 1 1 1 0 1 1 1 +V --| |-| |-| |-| |-| |-| |-| |-| 0 |-| |-| |-| |-| |-| |-| |-| |-| |-| |- -V |-| |-| ``` #### Manchester ```text 1 1 0 1 1 1 0 1 1 1 +V |-| |---| |-| |-| |---| |-| |-| |- 0 | | | | | | | | | | | | | | | -V --| |-| |---| |-| |-| |---| |-| |-| ``` #### Bipolar AMI ```text 1 1 0 1 1 1 0 1 1 1 +V ----| |---| |---| |---| 0 | |---| | | |---| | | -V |---| |---| |---| |--- ``` AMI pulse sequence: + - 0 + - + 0 - + - (the 1s alternate +, -, +, -, ...). ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why does line coding need transitions? A. For clock recovery B. To increase DC C. To lower cost only D. To remove bits Answer: A. Synchronisation. (Key point: Need) 2. Why remove the DC component? A. It adds bandwidth B. Transformers/AC-coupled links cannot pass it C. It carries clock D. It improves security Answer: B. DC blocked. (Key point: DC) 3. AMI pulses for 1101110111: A. + + 0 + + + 0 + + + B. + - 0 - + - 0 + - + C. + - 0 + - + 0 - + - D. + - 0 + - + 0 + - + Answer: C. 1s alternate. (Key point: AMI) 4. In the stated convention a 1 in Manchester is: A. High-to-low B. No transition C. Always high D. Low-to-high mid-bit transition Answer: D. Convention. (Key point: Manchester) ## Related in Data Communication - [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 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× - [Polar, unipolar, bipolar, Manchester; encode 101000111011](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-101000111011) — Data Communication, chapter 5 - [Encode 1001101110 with unipolar, polar, bipolar codes](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-1001101110) — Data Communication, chapter 5, asked 3× - [Encode 10110001110 with unipolar, polar, bipolar codes](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-10110001110-68c) — Data Communication, chapter 5, asked 3× ## Related in other subjects - [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 10110101 (polar NRZ, unipolar RZ, AMI, Manchester)](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aline-codes-10110101) — Communication Systems, chapter 6, asked 8× - [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×