The PA-VXB and PA-VXC are single-width port adapters with two universal ports that are configurable for either T1 or E1 connections. The PA-VXB contains 12 high-performance digital signal processors (DSPs) that support up to 48 medium-complexity or 24 high-complexity channels of compressed voice. The PA-VXC contains 30 high-performance DSPs that support up to 120 medium-complexity or 60 high-complexity channels of compressed voice.In Voice over IP, the DSP segments the voice signal into frames, which are then coupled in groups of two and stored in voice packets. These voice packets are transported using IP in compliance with ITU-T specification H.323. Because Voice over IP is a delay-sensitive application, you must have a well-engineered end-to-end network to use it successfully. Fine-tuning your network to adequately support Voice over IP involves a series of protocols and features geared toward quality of service (QoS). Traffic shaping considerations must be taken into account to ensure the reliability of the voice connection.