The Cisco® Packet Voice Digital Signal Processor Modules (PVDMs) enable Cisco 4000 Series Integrated Services Routers (ISRs) to provide rich-media capabilities such as high-density voice connectivity, conferencing, transcoding, media optimization, transrating, and secure voice for Cisco Unified Communications solutions. These new modules support unprecedented scale while allowing for a smaller solution footprint than ever before.

The PVDMs support digital voice connections, conferencing, universal transcoding, and media optimization services:
- T1/E1 voice: One of the primary uses of PVDMs is to packetize digital voice into IP packets to enable time-division multiplexing (TDM) digital voice applications.
- Conferencing: PVDM modules support ad hoc and meet-me conferencing with various codecs in conjunction with Cisco Unified Communications Manager and Cisco Unified Communications Manager Express.
- Universal transcoding: In conjunction with Cisco IOS® Software, the PVDMs support universal transcoding, which allows conversion from any supported codec to any other supported codec.
- Transrating: The PVDMs support transrating, in which the same codec is repacketized in order to connect dissimilar networks that have different codec packetization periods.
- Voice-quality management: The PVDMs perform compression, voice-activity detection, jitter management, and echo cancellation. The echo cancellation offered in the PVDMs has a tail length of 128 milliseconds and complies with ITU-T G.168.
- Energy savings: The motherboard PVDMs (PVDM4s) offer multiple power-saving modes, including a power-saver mode when the module is not in use. In power-saver mode, each PVDM4 can save up to 5 watts of power.

The analog voice modules (FXS, FXO, and E/M) and Basic Rate Interface (BRI) digital voice modules for the 4000 Series ISRs contain built-in, nonconfigurable digital signal processors (DSPs) and do not require any additional PVDMs for voice packetization.