--- title: "Line coding: properties; encode 01001100011" subject: "Data Communication" chapter: 5 key: "semester_5/data_communication:line-coding-01001100011" source: https://www.bctengineer.com/q/semester_5/data_communication/line-coding-01001100011 site: BCT Engineering --- # Line coding: properties; encode 01001100011 Data Communication · Chapter 5: Data Encoding and Modulation - Asked in: 2070 Asar, 3+8 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-01001100011 - Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-5 ## Question What is line coding? What are the desired properties of a line code? Encode the bit stream 01001100011 using the following encoding schemes: Unipolar NRZ-L, Unipolar NRZ-I, Unipolar RZ, Polar NRZ-L, polar NRZ-I, polar RZ, Manchester, and Alternate Mark Inversion (AMI). ## Short answer Unipolar NRZ-L: 1=+V, 0=0V; NRZ-I: toggle at 1, start low; RZ: 1=+V half-bit, 0=0V. Polar NRZ-L: 1=+V, 0=-V; NRZ-I: toggle at 1; RZ: 1=+V half-bit, 0=-V half-bit. Manchester: 1=low-to-high, 0=high-to-low mid-transition. AMI: 0=0V, 1s alternate ±V: 0+00-+000-+. ## Answer #### Line coding Line coding is the conversion of digital data (bits) into a digital signal (voltage levels) for transmission. #### Desired properties of a line code 1. **No DC component** (or small), so it passes through transformers and AC-coupled links. 2. **Self-synchronisation**: enough transitions so the receiver can recover the clock, even for long runs of 0s or 1s. 3. **Narrow bandwidth** (low baud rate for the data rate). 4. **Error detection** capability (for example AMI violations). 5. **Noise immunity** and low error rate. 6. **Low cost and simplicity**, with no ambiguity in decoding. 7. Polarity insensitivity (as in NRZ-I and differential Manchester). #### Encoding of 0 1 0 0 1 1 0 0 0 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. #### Unipolar NRZ ```text 0 1 0 0 1 1 0 0 0 1 1 +V |---| |-------| |------- 0 ----| |-------| |-----------| ``` #### Unipolar NRZ-I ```text 0 1 0 0 1 1 0 0 0 1 1 +V |-----------| |---------------| |--- 0 ----| |---| |---| ``` #### Unipolar RZ ```text 0 1 0 0 1 1 0 0 0 1 1 +V |-| |-| |-| |-| |-| 0 ----| |---------| |-| |-------------| |-| |- ``` #### Polar NRZ-L ```text 0 1 0 0 1 1 0 0 0 1 1 +V |---| |-------| |------- 0 | | | | | -V ----| |-------| |-----------| ``` #### Polar NRZ-I ```text 0 1 0 0 1 1 0 0 0 1 1 +V |-----------| |---------------| |--- 0 | | | | | -V ----| |---| |---| ``` #### Polar RZ ```text 0 1 0 0 1 1 0 0 0 1 1 +V |-| |-| |-| |-| |-| 0 |-| |-| |-| |-| |-| |-| |-| |-| |-| |-| |- -V --| |-| |-| |-| |-| |-| ``` #### Manchester ```text 0 1 0 0 1 1 0 0 0 1 1 +V --| |---| |-| |-| |---| |-| |-| |-| |- 0 | | | | | | | | | | | | | | | | -V |---| |-| |---| |-| |-| |-| |---| |-| ``` #### Bipolar AMI ```text 0 1 0 0 1 1 0 0 0 1 1 +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. What is line coding? A. Converting analog signals to bits by sampling B. Converting digital data (bits) into a digital signal of voltage levels for transmission C. Compressing data before transmission D. Modulating a carrier with data Answer: B. Line coding maps bits to voltage levels of a digital signal for the channel. (Key point: Line coding definition) 2. Why is self-synchronisation a desired line-code property? A. It removes the DC component B. It reduces bandwidth C. Enough transitions let the receiver recover the clock even for long runs of 0s or 1s D. It lets the receiver correct errors Answer: C. Transitions in the signal let the receiver stay in sync without a separate clock. (Key point: Self-synchronisation) 3. Why is a small or zero DC component desired? A. It increases the data rate B. The signal can pass through transformers and AC-coupled links C. It makes decoding ambiguous D. It makes the clock easier to recover Answer: B. Transformers and AC-coupled links block DC, so signals with large DC content get distorted. (Key point: No DC component) 4. For 0 1 0 0 1 1 0 0 0 1 1, what are the AMI pulses? A. 0 + 0 0 - + 0 0 0 - + B. 0 + 0 0 + + 0 0 0 + + C. 0 + 0 0 - + 0 0 0 + - D. 0 - 0 0 + - 0 0 0 + - Answer: A. The five 1s alternate +, -, +, -, + starting with +, giving 0 + 0 0 - + 0 0 0 - +. (Key point: AMI pulses) ## Related in Data Communication - [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× - [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 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× - [Polar, unipolar, bipolar, Manchester; encode 101000111011](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aline-coding-101000111011) — 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 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×