VDV Voice Systems 2

Question 1

Which signaling protocol is used between a PBX and the PSTN to set up and tear down calls?

Accepted Answer

ISDN PRI

Answer

ISDN PRI (Primary Rate Interface) is the most common digital signaling protocol connecting a PBX to the PSTN for call setup and teardown.

Question 2

What is the purpose of a codec in a VoIP system?

Accepted Answer

To encode and decode analog voice into digital packets

Answer

A codec (coder-decoder) converts analog voice signals into compressed digital data for transmission and reverses the process at the receiving end.

Question 3

What does the term 'jitter' refer to in VoIP communications?

Accepted Answer

Variation in packet arrival times

Answer

Jitter is the variation in arrival times of packets, which can cause choppy or distorted audio if not compensated by a jitter buffer.

Question 4

Which G-series codec provides toll-quality voice at 64 Kbps using PCM encoding?

Accepted Answer

G.711

Answer

G.711 is the standard PCM codec operating at 64 Kbps that defines toll-quality voice used in traditional PSTN and VoIP networks.

Question 5

A VDV technician is troubleshooting one-way audio on a VoIP call. Which firewall issue is the most likely cause?

Accepted Answer

NAT not translating RTP media streams

Answer

One-way audio in VoIP is commonly caused by NAT failing to properly translate the RTP (Real-Time Protocol) media stream IP addresses.

(VDV) Voice Data Video Technician Certified Practice Test