--- title: "Line coding 10110101 (polar NRZ, unipolar RZ, AMI, Manchester)" subject: "Communication Systems" chapter: 6 key: "semester_6/communication_systems:line-codes-10110101" source: https://www.bctengineer.com/q/semester_6/communication_systems/line-codes-10110101 site: BCT Engineering --- # Line coding 10110101 (polar NRZ, unipolar RZ, AMI, Manchester) Communication Systems · Chapter 6: Baseband Digital Data Transmission - Asked in: 2075 Asoj (CS II), 6 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 Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/communication_systems/line-codes-10110101 - Whole chapter: https://www.bctengineer.com/md/semester_6/communication_systems/chapter-6 ## Question Represent binary sequence 10110101 in Polar NRZ, unipolar RZ, AMI and Manchester codes. ## Short answer For 10110101, Polar NRZ: +V,-V,+V,+V,-V,+V,-V,+V. Unipolar RZ: +V,0 for first half for 1s, else 0. AMI: +V,0,-V,+V,0,-V,0,+V. Manchester: +V,-V,-V,+V,+V,-V,+V,-V,-V,+V,+V,-V. ## Answer Conventions (bit period $T_b$, amplitude $V$): - **Polar NRZ:** 1 → $+V$, 0 → $-V$ for the whole bit. - **Unipolar RZ:** 1 → $+V$ for the first half bit then 0; 0 → 0. - **AMI:** 0 → 0; 1s alternate $+V$, $-V$ (first 1 positive, full-width pulses; an RZ version with half-width pulses is also used). - **Manchester:** 1 → $+V$ then $-V$; 0 → $-V$ then $+V$ (transition at the middle of every bit). Bit sequence: **1 0 1 1 0 1 0 1** ```text bits 1 0 1 1 0 1 0 1 Polar NRZ: +V |‾‾‾‾ ‾‾‾‾‾‾‾‾ ‾‾‾‾ ‾‾‾‾ 0 | -V | ____ ____ ____ Unipolar RZ: +V |‾‾ ‾‾ ‾‾ ‾‾ ‾‾ 0 | ------ -- ------ ------ -- AMI (bipolar NRZ): +V |‾‾‾‾ ‾‾‾‾ ‾‾‾‾ 0 | ---- ---- ---- -V | ____ ____ Manchester: +V |‾‾ ‾‾‾‾ ‾‾ ‾‾‾‾ ‾‾‾‾ 0 | -V | ____ __ ____ ____ __ ``` Levels in each bit (a pair means first half, second half): | Code | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | |---|---|---|---|---|---|---|---|---| | Polar NRZ | +V | −V | +V | +V | −V | +V | −V | +V | | Unipolar RZ | +V,0 | 0 | +V,0 | +V,0 | 0 | +V,0 | 0 | +V,0 | | AMI (bipolar NRZ) | +V | 0 | −V | +V | 0 | −V | 0 | +V | | Manchester | +V,−V | −V,+V | +V,−V | +V,−V | −V,+V | +V,−V | −V,+V | +V,−V | | Code | DC component | Clock content | Bandwidth (first null) | |---|---|---|---| | Polar NRZ | Yes (if 1s and 0s unequal) | Poor in long runs | $R_b$ | | Unipolar RZ | Yes | Good for 1s, none for 0s | $2R_b$ | | AMI | None | Poor for runs of 0s | $R_b$ | | Manchester | None | Excellent | $2R_b$ | ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. In AMI coding, how are bits represented? A. 0 as 0; 1s alternate between +V and -V B. 1 as 0; 0s alternate C. 1 always +V D. 0 as -V Answer: A. Alternating 1s give zero DC and let violations reveal errors. (Key point: AMI rule) 2. For 10110101 the AMI levels are: A. +V 0 -V +V 0 -V 0 +V B. +V 0 +V +V 0 +V 0 +V C. +V 0 -V -V 0 +V 0 -V D. -V 0 +V -V 0 +V 0 -V Answer: A. The five 1s alternate +, -, +, -, + starting with +V. (Key point: AMI for the sequence) 3. In Unipolar RZ, a 1 is sent as: A. +V for the full bit B. +V for the first half, then 0 C. -V for the first half D. 0 then +V Answer: B. Bit 0 is 0 throughout; bit 1 is +V for half a bit and returns to zero. (Key point: Unipolar RZ) 4. Which code has no DC component and excellent clock content but needs 2Rb bandwidth? A. Polar NRZ B. Unipolar RZ C. Manchester D. AMI Answer: C. Manchester has a mid-bit transition in every bit and zero average, at twice the NRZ bandwidth. (Key point: Bandwidth and DC) ## Close variants set in other exams - [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 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 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 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× - [Line coding 1101010011 (polar NRZ, polar RZ, Manchester, AMI)](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aline-codes-1101010011) — Communication Systems, chapter 6, asked 8× ## Related in Communication Systems - [Line coding 100111010 (Polar RZ, bipolar NRZ, AMI, Manchester)](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aline-codes-100111010) — Communication Systems, chapter 6 - [Line coding 1011000010000000001 (polar NRZ, AMI, Manchester)](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aline-codes-polar-ami-manchester-long) — Communication Systems, chapter 6, asked 2× - [Definitions of unipolar, polar, bipolar, RZ, Manchester codes](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Adefine-line-codes) — Communication Systems, chapter 6, asked 2× - [Line coding 110011000001 (unipolar RZ, Manchester, HDB3)](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aline-codes-110011000001) — Communication Systems, chapter 6 ## Related in other subjects - [Line coding and NRZ, RZ, AMI](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aline-coding-nrz-rz-ami) — Telecommunications, chapter 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 - [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×