Voice Systems Flashcards
7 cards from real VDV practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Voice Systems flashcards as text
Which signaling protocol is used between a PBX and the PSTN to set up and tear down calls?
Answer: ISDN PRI
ISDN PRI (Primary Rate Interface) is the most common digital signaling protocol connecting a PBX to the PSTN for call setup and teardown.
What is the purpose of a codec in a VoIP system?
Answer: To encode and decode analog voice into digital packets
A codec (coder-decoder) converts analog voice signals into compressed digital data for transmission and reverses the process at the receiving end.
What does the term 'jitter' refer to in VoIP communications?
Answer: Variation in packet arrival times
Jitter is the variation in arrival times of packets, which can cause choppy or distorted audio if not compensated by a jitter buffer.
Which G-series codec provides toll-quality voice at 64 Kbps using PCM encoding?
Answer: G.711
G.711 is the standard PCM codec operating at 64 Kbps that defines toll-quality voice used in traditional PSTN and VoIP networks.
A VDV technician is troubleshooting one-way audio on a VoIP call. Which firewall issue is the most likely cause?
Answer: NAT not translating RTP media streams
One-way audio in VoIP is commonly caused by NAT failing to properly translate the RTP (Real-Time Protocol) media stream IP addresses.
What is the standard impedance for analog telephone loop circuits in North America?
Answer: 600 ohms
The standard impedance for analog telephone circuits in North America is 600 ohms, which is used for proper impedance matching to minimize signal reflections.
Which feature allows a single phone number to ring multiple devices simultaneously in a VoIP system?
Answer: Simultaneous ring / Find Me Follow Me
Simultaneous ring (also called Find Me Follow Me) causes multiple registered devices to ring at once when a single number is dialed.