---
title: "RS-232C importance; time to transmit a string at 4800 baud"
subject: "Instrumentation II"
chapter: 3
key: "semester_5/instrumentation_ii:rs232c-string-time-4800"
source: https://www.bctengineer.com/q/semester_5/instrumentation_ii/rs232c-string-time-4800
site: BCT Engineering
---

# RS-232C importance; time to transmit a string at 4800 baud

Instrumentation II · Chapter 3: Serial Interfacing With Microprocessor Based System

- Asked in: 2075 Asoj, 2+4 marks
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/instrumentation_ii/rs232c-string-time-4800
- Whole chapter: https://www.bctengineer.com/md/semester_5/instrumentation_ii/chapter-3

## Question

What is the importance of RS232-C in serial communication? Determine the time required to transmit a string: "Life is beautiful." using asynchronous serial data transfer method in baud rate of 4800 Baud. Suppose a character has 7 bits data, one bit start bit, one bit stop bit and one bit even parity bit.

## Short answer

RS-232C standardizes voltage levels (±3–15 V), DB-9/DB-25 connectors, and handshaking for DTE–DCE links. The string "Life is beautiful." has 18 characters; each 10‑bit frame (1 start + 7 data + 1 parity + 1 stop) gives 180 bits. At 4800 baud, time = 180/4800 = 37.5 ms.

## Answer

#### Importance of RS-232C
RS-232C is the standard serial interface between a DTE (computer) and a DCE (modem) or other serial equipment. It defines electrical levels (mark -3 to -15 V, space +3 to +15 V), connector (DB-25/DB-9), signal functions (TXD, RXD, RTS, CTS, DSR, DTR) and handshaking. It gives a simple, cheap, universal way to connect PCs, modems, printers and microcontroller boards using only a few wires.

#### Time to transmit "Life is beautiful."
Characters: "Life" (4) + space (1) + "is" (2) + space (1) + "beautiful" (9) + "." (1) = **18 characters**.
Frame = 1 start + 7 data + 1 even parity + 1 stop = **10 bits**.
```text
 Total bits = 18 x 10 = 180 bits
 Time       = 180 / 4800 = 0.0375 s
```
**Answer: 37.5 ms** (character time 2.083 ms, 480 characters/s).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Characters in 'Life is beautiful.'?
   A. 18
   B. 16
   C. 17
   D. 15
   Answer: A. 4+1+2+1+9+1 = 18. (Key point: Characters)

2. Bits per character with start, 7 data, even parity, stop?
   A. 11
   B. 9
   C. 10
   D. 8
   Answer: C. 1+7+1+1 = 10. (Key point: Frame bits)

3. Total time at 4800 baud?
   A. 3.75 ms
   B. 75 ms
   C. 37.5 ms
   D. 18 ms
   Answer: C. 180/4800 = 37.5 ms. (Key point: Time)

## Related in Instrumentation II

- [Bit rate, baud rate and character time at 9600](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Abaud-time-engineer) — Instrumentation II, chapter 3
- [Asynchronous serial transfer of a character](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Aasync-7bit-ascii-2stop) — Instrumentation II, chapter 3
- [Character transmission time at 1200 baud](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Abaud-time-1200) — Instrumentation II, chapter 3, asked 2×
- [RS-422A vs RS-232C distance and speed](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Ars422-vs-rs232-distance) — Instrumentation II, chapter 3, asked 3×