Specifications

2-46
Cisco IGX 8400 Series Provisioning Guide, Release 9.3.3 and Later Releases
OL-1166-04
Chapter 2 Cisco IGX 8400 Series Cards
Channelized Voice Module
Tip Voice compression ratios approximately double when you enable internal VAD on that channel.
Idle Code Suppression on the CVM
Idle code suppression (ICS) allows bandwidth savings on an nx64 super-rate data connection used to
carry video traffic conforming to the H.221 video codec frame protocol. The video channel is considered
idle at any time when identical data occurs in relevant time slots for 256 consecutive T1, E1, or J1
frames. Depending on the data channel size, the number of consecutive identical bytes necessary to
trigger idle code suppression can range from 256 to 2048 consecutive identical byes.
To enable ICS on a data channel, use the switch software cnfdch command.
Tip In order to configure ICS on a data channel, the data channel must be used in an nx64 super-rate data
connection that terminates on either a UVM or a CVM.
CVM Front Cards
The CVM has three different front card options: standard CVM, CVM T1 EC, and CVM E1 EC.
The standard CVM supports the features listed in the “Channelized Voice Module” section on page 2-44.
The CVM T1 EC features on-board echo cancelling circuitry for T1 lines. The CVM E1 EC features
on-board echo cancelling circuitry for E1 lines.
CVM Back Cards
The CVM has three different back cards. Please refer to the “CVM Front Cards” section on page 2-46
for compatibility requirements.
T1 Interface Back Card (BC-T1)
The BC-T1 back card provides a T1 line interface for a CVM front card. The BC-T1 back card has the
following features:
• One T1 line physical interface using a DB-15 connector
• Support for both CAS and CSS
• A transmission speed of 1.544 Mbps
• Software-selectable AMI or B8ZS line code
Table 2-30 Voice Compression Ratios According to Channel Transmission Rates
Transmission Rate Voice Compression Ratio
64 kbps Voice traffic is not compressed
32 kbps 2:1
24 kbps 8:3 (~ 2.66:1)
16 kbps 4:1