The most commonly used companding (that is, COMpressing exPANDING) algorithm in North America and Japan, which has lower idle channel noise compared to a-Law companding.
Uninterruptible Power Supply (UPS)
A power backup device that allows network components to continue functioning in the event of a power failure.
Unity
The Cisco flagship converged messaging solution, offering a single repository for voice, e-mail, and fax messages.
Unity PBX-IP Media Gateway (PIMG)
A device that allows a Cisco Unity messaging system to be used in a legacy PBX environment.
user agent (UA)
A SIP device that contains call-forwarding intelligence, such as a User Agent Client (that is, a SIP device that places calls) or a User Agent Server (that is, a SIP device that receives a call).
