How does signaling differ between traditional telephone calls and PacketCable VoIP calls?

How does signaling differ between traditional telephone calls and PacketCable VoIP calls?

• A. Traditional PSTN signaling is initiated when central office equipment senses a dial tone; PacketCable VoIP signaling is initiated when the EMTA senses a dial tone
• B. Traditional PSTN signaling is manual; PacketCable VoIP signaling is automatic by the network
• C. Traditional PSTN signaling uses IP; PacketCable VoIP signaling uses circuit signaling
• D. Traditional PSTN signaling starts after the caller presses dial; PacketCable VoIP signaling starts after call acceptance

Answer: (A)

Signaling starts at different places in the two systems. In a traditional PSTN, the central office is the one that detects that the line is ready by providing dial tone, and once the user starts dialing, the CO’s switching system takes over with the call setup signaling. In PacketCable VoIP, the edge device at the customer premises—the EMTA—handles the initial cues, including noticing when the user lifts the handset and hears dial tone, and it begins the IP-based signaling to establish the call on the network. So the difference is where the signaling is triggered: centralized in the PSTN by the CO, versus edge-triggered in the VoIP system by the EMTA. This aligns with the idea that PSTN signaling starts when the central office senses readiness (dial tone), while PacketCable VoIP signaling starts when the EMTA senses dial tone and initiates IP signaling to set up the call.

Signaling starts at different places in the two systems. In a traditional PSTN, the central office is the one that detects that the line is ready by providing dial tone, and once the user starts dialing, the CO’s switching system takes over with the call setup signaling. In PacketCable VoIP, the edge device at the customer premises—the EMTA—handles the initial cues, including noticing when the user lifts the handset and hears dial tone, and it begins the IP-based signaling to establish the call on the network. So the difference is where the signaling is triggered: centralized in the PSTN by the CO, versus edge-triggered in the VoIP system by the EMTA. This aligns with the idea that PSTN signaling starts when the central office senses readiness (dial tone), while PacketCable VoIP signaling starts when the EMTA senses dial tone and initiates IP signaling to set up the call.