---
title: "Compare RS-232C, RS-422A and RS-423A"
subject: "Instrumentation II"
chapter: 3
key: "semester_5/instrumentation_ii:rs232-422-423-compare"
source: https://www.bctengineer.com/q/semester_5/instrumentation_ii/rs232-422-423-compare
site: BCT Engineering
---

# Compare RS-232C, RS-422A and RS-423A

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

- Asked in: 2070 Chaitra, 4 marks
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/instrumentation_ii/rs232-422-423-compare
- Whole chapter: https://www.bctengineer.com/md/semester_5/instrumentation_ii/chapter-3

## Question

Compare between RS 232C, RS422A and RS423A.

## Short answer

RS-232C is single-ended with ±5 to ±15V levels, max 20kbps and 15m. RS-422A is differential, up to 10 receivers, 10Mbps at 12m, 1200m at 100kbps. RS-423A uses single-ended driver with differential receiver, reaching 100kbps over 90m and 1200m at 1kbps.

## Answer

| Parameter | RS-232C | RS-422A | RS-423A |
|---|---|---|---|
| Signalling | Single-ended, unbalanced | Differential, balanced | Single-ended, unbalanced (differential receiver) |
| Drivers / receivers | 1 driver, 1 receiver | 1 driver, up to 10 receivers | 1 driver, up to 10 receivers |
| Line voltage | +/-5 to +/-15 V (driver); receiver +/-3 V | +/-2 to +/-6 V differential | +/-4 to +/-6 V |
| Receiver sensitivity | +/-3 V | 200 mV | 200 mV |
| Max. data rate | 20 kbps | 10 Mbps (at 12 m) | 100 kbps |
| Max. distance | about 15 m | 1200 m (at 100 kbps) | 1200 m (at 1 kbps), 90 m at 100 kbps |
| Cable | Multicore, shielded | Twisted pair | Shielded |
| Noise immunity | Poor | Very good | Medium |
| Wires per signal | 1 + common ground | 2 (pair) | 1 + common signal ground |
| Termination | None | 100-120 ohm | Not needed (optional) |
| Use | PC serial ports, modems | Long, fast, noisy industrial links | Intermediate upgrade of RS-232C |

## Check yourself

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

1. Which is differential and balanced?
   A. RS-423A
   B. All three
   C. RS-422A
   D. RS-232C
   Answer: C. RS-422A uses twisted pairs with differential signalling; RS-232C and RS-423A are single-ended. (Key point: Signalling)

2. How many receivers can RS-232C drive?
   A. 10
   B. 100
   C. 32
   D. 1
   Answer: D. RS-232C is one driver and one receiver; RS-422A and RS-423A allow up to 10. (Key point: Receivers)

3. Which has the highest maximum data rate?
   A. All same
   B. RS-232C 20 kbps
   C. RS-422A 10 Mbps
   D. RS-423A 100 kbps
   Answer: C. RS-422A reaches 10 Mbps at 12 m. (Key point: Distance and rate)

4. Why is RS-422A more noise immune?
   A. No cable
   B. Balanced differential pair rejects common-mode noise
   C. Higher single-ended voltage
   D. No termination
   Answer: B. Noise appears equally on both wires of the pair and cancels at the differential receiver. (Key point: Noise immunity)

## Related in Instrumentation II

- [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×
- [RS-232C handshaking signals](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Ars232-handshake-signals) — Instrumentation II, chapter 3, asked 2×
- [Importance and working of RS-232C](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Ars232c-importance-signals) — Instrumentation II, chapter 3
- [RS-232C importance; time to transmit a string at 4800 baud](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Ars232c-string-time-4800) — Instrumentation II, chapter 3