PDH Knowledge Test

30 Questions on Plesiochronous Digital Hierarchy

Test Instructions

This assessment covers fundamental concepts of Plesiochronous Digital Hierarchy (PDH). Try to answer each question before revealing the solution.

The test includes multiple-choice and true/false questions
Topics cover PDH fundamentals, hierarchies, frame structures, and limitations
Click the "Show Answer" button to reveal the correct response
Key terms are highlighted in blue and important concepts in red

What does the "P" in PDH stand for?

A) Parallel

B) Plesiochronous

C) Packet

D) Phase

Correct Answer: B) Plesiochronous

What is the meaning of "plesiochronous"?

A) Perfectly synchronized

B) Completely asynchronous

C) Almost synchronous

D) Phase-aligned

Correct Answer: C) Almost synchronous

What is the bit rate of an E1 signal?

A) 1.544 Mbps

B) 2.048 Mbps

C) 8.448 Mbps

D) 34.368 Mbps

Correct Answer: B) 2.048 Mbps

How many 64 kbps channels are in a T1 signal?

A) 24

B) 30

C) 32

D) 28

Correct Answer: A) 24

What technique does PDH use to handle timing differences between signals?

A) Phase locking

B) Bit stuffing

C) Frequency scaling

D) Time slicing

Correct Answer: B) Bit stuffing

Which PDH level comes after E3 in the hierarchy?

A) E2

B) E4

C) E5

D) E1

Correct Answer: B) E4

What is the primary limitation of PDH that led to the development of SDH/SONET?

A) Limited bandwidth capacity

B) Lack of standardization between regions

C) Complex add/drop multiplexing

D) All of the above

Correct Answer: D) All of the above

Which time slot in E1 is used for frame alignment?

A) Time slot 0

B) Time slot 1

C) Time slot 16

D) Time slot 31

Correct Answer: A) Time slot 0

How many E1 signals are multiplexed to form an E2 signal?

A) 2

B) 3

C) 4

D) 5

Correct Answer: C) 4

What is the bit rate of a T3 signal?

A) 34.368 Mbps

B) 44.736 Mbps

C) 139.264 Mbps

D) 155.520 Mbps

Correct Answer: B) 44.736 Mbps

Which region primarily used the E-carrier system?

A) North America

B) Europe

C) Japan

D) Australia

Correct Answer: B) Europe

What is the frame duration in PDH systems?

A) 64 μs

B) 125 μs

C) 250 μs

D) 500 μs

Correct Answer: B) 125 μs

How many bits are in a standard E1 frame?

A) 192 bits

B) 256 bits

C) 512 bits

D) 1024 bits

Correct Answer: B) 256 bits (32 time slots × 8 bits)

What is the primary function of bit stuffing in PDH?

A) Error correction

B) Synchronization of different clock rates

C) Data encryption

D) Signal amplification

Correct Answer: B) Synchronization of different clock rates

Which of the following is NOT a PDH level?

A) E3

B) T2

C) OC-3

D) DS1

Correct Answer: C) OC-3 (This is an SONET level)

True or False: PDH allows direct access to individual channels without demultiplexing the entire signal.

A) True

B) False

Correct Answer: B) False (This is a key advantage of SDH over PDH)

What is the bit rate of an E4 signal?

A) 34.368 Mbps

B) 44.736 Mbps

C) 139.264 Mbps

D) 565.148 Mbps

Correct Answer: C) 139.264 Mbps

Which time slot in E1 is typically used for signaling?

A) Time slot 0

B) Time slot 1

C) Time slot 16

D) Time slot 31

Correct Answer: C) Time slot 16

What is the fundamental channel rate in digital telephony?

A) 32 kbps

B) 64 kbps

C) 128 kbps

D) 256 kbps

Correct Answer: B) 64 kbps (DS0 channel)

Which multiplexing technique is used in PDH?

A) Time Division Multiplexing (TDM)

B) Frequency Division Multiplexing (FDM)

C) Wavelength Division Multiplexing (WDM)

D) Code Division Multiplexing (CDM)

Correct Answer: A) Time Division Multiplexing (TDM)