Section 2 RS-232

Question 1

What is RS-232?

Answer 1

The most popular standard for serial communication between DTE and DCE

Question 2

What are the signal voltage levels for RS-232 (TX and RX)?

Answer 2

The voltage levels for RS-232 are between 5 and 15V (Space 0) and -5 and -15V (Mark 1) at the transmitter. Receiver gets 3 to 15V for Space and -3 to -15V for Mark.

Question 3

What is usually connected to the female DB-25 connector? What is usually connected to the
male DB-25 connector?

Answer 3

Female DB-25 connector is for DCE and the male DB-25 connector is for DTE

Question 4

List two major disadvantages associated with RS-232?

Answer 4

1) The system is unbalanced
2) Unterminated
3) Single ended

These characteristics make the system slow and very short range

Question 5

What is the difference between balanced and unbalanced transmission systems? Why are balanced systems used more?

Answer 5

A balanced system is faster and allows for a longer range than the unbalanced system as it has 2 wires for each transmitting device.

Question 6

Describe the KEY circuit improvement which allows RS-422 to communicate faster and over
greater distance than RS-423?

Answer 6

A pair of wires at each transmitting device

Question 7

What is the most efficient error detection method and how does it work?

Answer 7

Cyclic Redundancy Checking